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No Data


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Solar X-Ray flux
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Geomagnetic Alert
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Polar Cap Absorption

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N/A Solar X-Rays
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MainHF Radio Resource CenterHF & Space Weather Panel

Welcome to the HF and Space Weather Panel, a resource to study the physics and magnetic interaction between the Sun and the Earth and the propagation status in the HF bands, with applications to radio communications.

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Current Space Weather

Solar Wind
No Data No Data No Data No Data
Interplanetary Magnetic Field (IMF) and Solar Ionosphere Potential
No Data No Data No Data No Data

Current space weather. Source: Rice University

No Data

Satellite environment plot. Source: NOAA/SWPC

 

Last data of solar activity and geomagnetism. Source: SIDC

 


Table of Contents




Solar
Activity


Sun-Earth
Interaction


Solar Radiation
Storms



Geomagnetic
Storms


Ionosphere Status


Radio Communications


Aurorae


Bulletins


Links


Remarks


HF Glossary (ESP)

User's Manual (ESP)


HF Central

Technical Articles


EA4FSI Home


Contact Form

 

 


 



Solar Activity

Solar X-Rays | Reports | Pictures of the Sun | Solar Flux Index and Sunspots

 

No Data

Latest solar X-ray image - Updated every 5 minutes
Source: NOAA/SWPC - GOES spacecraft

 


Actividad Solar


Solar X-Ray Flux

The Earth is subject to the radiation coming from the Sun. Part of this radiation is ionizing and can excite the oxygen and hydrogen molecules in the ionosphere, causing them to oscillate. This oscillation may cause those molecules to be dissociated into two atoms or even those atoms to detach some of their electrons. The most ionizing radiations generated by the Sun are within the range of the UV-rays (wavelength between 20-300 angstroms) and the X-Rays (wavelength between 8-20 angstroms). The electron density in the ionosphere increases, causing radio waves absorption in the HF band, making communications difficult to establish and even total radio fadeouts. The following graph shows real-time data of the ionizing radiation density flux in the X-Ray band, coming from the Sun and measured by the NASA GOES spacecrafts. The solar X-ray image shown is the last one taken by the GOES-15 spacecraft.

No Data

Current solar X-ray flux - Updated every 5 minutes
Source: NOAA/SEC - GOES Spacecraft


The plots shows real-time data of the ionizing radiation density flux (watts per square meter) in the X-Ray band, measured by the GOES-15 spacecraft. The rightmost scale shows  the intensity of solar flares as a function of the measured radiation flux density: threshold A and B indicate normal flares. The C threshold is an indicator of a small solar flare, M is related to medium flares, X with big flares and over X indicates a so far unseen flare. The higher values are normally registered during periods of high solar activity within the 11 year solar cicle. The higher intensity of the solar X-Ray emission, the greater the attenuation due to absorption in the HF band. In case of a major solar flare, please check the Spectrum Monitors and the HF Absorption Levels, which may be significant during intervals of minutes to hours.

IPS: Recent flare and fadeout information (larger than C8 only).

 


Solar Activity


Solar Activity Reports

 

No Data
Solar activity level for the past month. Updated every 24 hours
Source: IPS Solar Activity Plot

 

 
Latest solar activity warnings and reports
Source: Big Bear Solar Observatory

 

 

Solar Activity


Pictures of the Sun

Current solar images taken every 10 seconds by the Atmospheric Image Assembly (AIS) instrument of the NASA's Solar Dynamics Observatory (SDO), at different wavelengths. For each picture, a high resolution version and a movie showing the last 48 hours pictures are available. Courtesy of NASA/SDO and the AIA, EVE, and HMI science teams.

 

No Data
SDO AIA 19.3 nm
High resolution | Video
No Data
SDO AIA 30.4 nm
High resolution | Video
No Data
SDO AIA 17.1 nm
High resolution | Video
No Data
SDO AIA 21.1 nm
High resolution | Video
No Data
SDO AIA 13.1 nm
High resolution | Video
No Data
SDO AIA 33.5 nm
High resolution | Video
No Data
SDO AIA 9.4 nm
High resolution | Video
No Data
SDO AIA 16.0 nm
High resolution | Video
No Data
SDO AIA 17.0 nm
High resolution | Video
  No Data
SDO AIA 45.0 nm
High resolution | Video
 

No Data
SDO AIA Com 211-193-171
High resolution

No Data
SDO AIA Com 304-211-171
High resolution

No Data
SDO AIA Com 094-335-193
High resolution

No Data
SDO AIA Com 181-HMI
High resolution

 

Pictures of the Sun taken by the SOHO's Extreme Ultraviolet Imaging Telescope (EIT), at different wavelenghts. Solar Data Analysis Center, NASA Goddard Space Flight Center. Click on each pìcture to see the high resolution version. Source: SOHO/NASA-ESA.

 

No Data
SOHO EIT 17.1 nm
High resolution | Video

No Data
SOHO EIT 19.5 nm
High resolution | Video

No Data
SOHO EIT 28.4 nm
High resolution | Video

No Data

SOHO EIT 30.4 nm
High resolution | Video

Images of the Sun taken by the SOHO's Large Angle Spectrometric Coronagraph (LASCO). C2 images show the inner solar corona up to 8.4 million kilometers (5.25 million miles) away from the Sun. C3 images show the outer solar corona up to 45 million kilometers (30 million miles) away from the Sun. Thanks to The coronagraphs, we are able to see the greatest solar flares and coronal mass ejections (CME) from the Sun. Click on each pìcture to see the high resolution version. Source: SOHO/NASA-ESA.


No Data
SOHO LASCO C2 (Inner solar corona)
High resolution | Video

No Data
SOHO LASCO C3 (Outer solar corona)
High resolution | Video

 

Coronameter image from the Mauna Loa Solar Observatory (Hawaii). The coronameter shows a clear view of the solar flares generating solar wind at very high speed.

 

 

No data

Latest solar corona image
Source: Mauna Loa Solar Observatory

 

 

 

Solar Activity


Solar Flux Index and Sunspots

Emission from the Sun at centimetric (radio) wavelength is due primarily to coronal plasma trapped in the magnetic fields overlying active regions. There is a direct relationship between the solar activity level and this emission, measured through the Solar Flux Index (SFI or F10.7). The SFI is a measure of the solar radio flux per unit frequency at a wavelength of 10.7 cm (2800 MHz). High values of SFI cause propagation openings in the higher HF bands.

 

No Data

SFI trend during the last days (red plot)
Source: NOAA/N0NBH

The plots show the trend of the following parameters during the last month:
- Green plot: proton flux measured at the line He II 30.4 nm (NASA SDO EVE).
- Blue plot: proton flux measured at the line He II 30.4 nm (NASA SOHO CELIAS SEM).
- Red plot: SFI measured by the Dominion Radio Astrophysical Observatory (Canada).
- Yellow plot: sunspot number (SN) measured by the Boulder Observatory (NOAA), Wolf number.

The SFI value is updated every day at 21:00 from the NOAA's WWV station.



Another way to check the activity of the Sun at a given instant is by means of quantifying the Sunspot Number (SSN), a process which can be performed following different methods. The sunspots are solar regions radiating approximately half the energy of  the rest of regions in the solar surface. The higher number of sunspots, the higher grade of ionization, causing the MUF to increase and making easier to establish ionospheric reflection radiocommunications in the higher HF bands. There is a strong correlation between the SFI and the SSN.

 

 

No Data

Current Michelson Doppler Imager (MDI) picture
Source: SOHO/NASA

 

The image shows the latest picture taken with the SOHO's MDI instrument, where the current sunspots and sunspot groups can be seen. During the solar cycle minimums the sunspot number is very small, to the point that in some cases there are no sunspots at all. Every solar cycle can be identified by the magnetic polarity of their sunspots: for a given solar hemisphere (North or South), all the sunpots have the same polarity during the cycle. The sunspots in the other hemisphere will have the opposite polarity during the same cycle. Every 11 years, when one cycle finishes and the next one begins, the Sun flips its magnetic polarity and the orientation of the sunspots is also inverted.

 

 

No Data

Latest FeXV 284Å EIT (Extreme UV Imaging Telescope) image
Source: SIDC & SOHO/NASA

The image shows the latest image of the Sun in the 284Å band, taken by the Extreme Ultraviolet Imaging Telescope (EIT) of the NASA's SOHO spacecraft, showing the NOAA regions and Catania sunspot groups. Click on the image to get a larger and interactive version providing detailed information about each sunspot shown.

The Mount Wilson Obsevatory in California provides the following sunspot classification:


Type Description
Alpha A unipolar sunspot group
Beta A sunspot group having both positive and negative magnetic polarities (bipolar), with a simple and distinct division between the polarities
Gamma A complex active region in which the positive and negative polarities are so irregularly distributed as to prevent classification as a bipolar group
Beta-Gamma A sunspot group that is bipolar but which is sufficiently complex that no single, continuous line can be drawn between spots of opposite polarities
Delta A qualifier to magnetic classes indicating that umbrae separated by less than 2 degrees within one penumbra have opposite polarity
Beta-Delta A sunspot group of general beta magnetic classification but containing one (or more) delta spot(s)
Beta-Gamma-Delta A sunspot group of beta-gamma magnetic classification but containing one (or more) delta spot(s)
Gamma-Delta A sunspot group of gamma magnetic classification but containing one (or more) delta spot(s)

 

The sunspot number is necessary as a parameter for many HF propagation calculators and can be presented in a variety of formats. A link to the NOAAA's National Geophysical Data Center (NGDC) pages follows, where you can get current data about the Sunspot Number in different formats, including ISN (International Sunspot Number, compiled by the Sunspot Index Data Center in Belgium), American Relative Sunspot Numbers, ancient sunspot data and Group Sunspot Numbers.




Remark for VOACAP users: please use the Smoothed International Sunspot Number (SSN) via this direct link: Smoothed International Sunspot Number at NGDC

 

No Data

No Data

Sunspot cycle - Updated once a month
Source: SIDC

The plots show the sunspot number evolution during the last years. This number follows periodic cycles of an estimated duration of 11 years. At the cycle peaks the sunspot number is higher and the propagation conditions are better. Due to the fact that some sunspots may appear grouped, the "Wolf number" is used in the computation, which takes into account both the groups and the isolated sunspots. We are currently at solar cycle 24.

 

 


 



Sun-Earth Interaction

Solar Wind and Interplanetary Magnetic Field | Magnetopause Status

 

No Data

Current solar wind data
Fuente: NOAA/SWPC


 

Sun-Earth Interaction


Solar Wind and Interplanetary Magnetic Field

The solar wind is made of electrically charged particles originated by solar flares, which are travelling at very high speed towards the Earth. Although the magnetosphere works as a protecting shield, in the cases of very intense solar flares, part of this wind hits the upper ionosphere, affecting radiocommunications in the HF and satellite bands.

 

No Data

Last data from SWEPAM (Solar Wind Electron, Proton and Alpha Monitor)
Source: NASA/NOAA - ACE spacecraft


Last 6 hours data of the following solar wind parameters: Temperature (ºK), speed (km/s), proton density (protons/cm3), angle between the IMF vector and the YZ plane in GSM coordinates (Phi, degrees) and Interplanetary Magnetic Field magnitudes (Bt, Bz). Please take a look here for further information.

 

No Data

Accumulated data of solar wind during the last 2 days
Source: Maryland University - SOHO Spacecraft


The Interplanetary Magnetic Field (IMF) is the name of the magnetic field created by the Sun. Due to the solar rotation (one complete rotation every 27 terrestrial days), it has an spiral shape. The Earth creates its own geomagnetic field, which works a a defensive shield against the solar wind and spreads through a region called magnetosphere. The region of the space in wich both magnetic fields interact is called magnetopause. If the IMF reaches the Earth following the southward direction, it can to a certain point cancel the Earth's magnetic field, making easier for the solar wind to reach the ionosphere and causing aurorae and geomagnetic storms.



No Data

IMF on the 'z' axis (Bz) - Updated every 2 min
Source: Solar Terrestrial Dispatch
No Data

IMF on the 'z' axis (Bz) - Updated every 2 min
Source: Solar Terrestrial Dispatch


The IMF is a vectorial field wich three dimensions named x, y, z, being the yz plane orthogonal to the plane of the ecliptic. Following this coordinate system, if the Bz component of the IMF is negative, the IMF points towards the South of the Earth anf if it is powerful enough it can cause a geomagnetic storm. The plots show the total IMF (Bt) and the IMF along the 'z' axis (Bz).

 

 

 

Sun-Earth Interaction


Magnetopause status

No Data

Magnetopause status.
Source: ISTP/PIXIE

The magnetopause is the separation interface between the magnetosphere and the interplanetary space. It is normally located at a distance of about 10 times the Earth's radius, towards the Sun. However, during high solar activity episodes, this distance may be reduced to about 6,6 times the Earth's radius.

In the figure, the Earth is in the center, and is illuminated from the left by the Sun (not shown). In this view, we are looking down upon the North pole; thus the figure represents the equatorial plane. The solar wind emanating from the Sun is super-magnetosonic with respect to the Earth, so that a shock wave is formed. As the solar wind flows through the shock it is slowed down, and the pressure of the solar wind is balanced by the pressure from the Earth's magnetic field. The boundary at which this pressure balance is achieved is called the magnetopause.

 

 

No hay datos

Current magnetopause position
Source: NASA - SWMF, T. Gombosi et al.


 

 



Solar Radiation Storms

SPE Monitors

 

N/A Solar Radiation Storm (Current)
N/A Solar Radiation Storm (Past 24 hours)

NOAA Alerts about Solar Radiation Storms
Source: NOAA/SWPC
NOAA Scale (pdf)

 

The Solar Proton Events (SPE) are originated when the protons emitted by the Sun are accelerated in its proximity after a solar flare, or in distant regions as an effect of the shock wave caused by a coronal mass ejection (CME). Those protons reach high energetic levels and after hitting the Earth can cause solar radiation storms. Those storms are originated between 15 minutes and several hours after a severe solar event and may have a duration of hours or even days, causing possible biological risks and affecting the satellite operations, radio communications and radionavigation systems.

In the HF band, attenuation levels of 1-4 dB each 1000 km may be reached. The attenuation can be extremely severe in transpolar radio paths, causing Polar Cap Absoprtion (PCA) events. If a solar radiation storm occurs, please check the HF Absorption Levels.


Solar Radiation Storms


Solar Proton Events (SPE) Monitors

The intensity of the solar radiation storms is quantified as a function of the measurement of the flux of particles (ions) with an energetic level greater that 10 MeV, coming from the Sun and originated in a SPE.

 

No Data

Energetic particles monitor - Data from the last 2 weeks
Source: University of Maryland - SOHO CELIAS/MTOF

The monitor shows the amount of energetic particles, according to the PM_Min formula. The solar wind with very high density or temperature can cause high values of PM_Min. However, it is considered that only values higher than 6000 are related to solar flares. In normal conditions (quiet solar wind), the values are under 100. The values higher than 100 indicate that a solar radiation storm is in progress.

 

No Data

Electron and proton density cummulative data during the last 24 hours
Source: NOAA/SWPC - ACE spacecraft

The plots show the measured proton and electron densities for each energetic range between 35 and 1900 MeV. All values increase during solar radiation storms. ACE RTWS EPAM stands for "Advanced Composition Explorer Real Time Solar Wind Energetic Ions and Electrons".

 


 

 



Geomagnetic Storms

Kp Index | Ap Index | Dst Index

 

N/A Geomagnetic Storm (Current)
N/A Geomagnetic Storm (Past 24 hours)

NOAA Alerts about Geomagnetic Storms
Source: NOAA/SWPC
NOAA Scale (pdf)
 

One to four days after a solar flare or a coronal mass ejection, a cloud of solar materials and their associated interplanetary magnetic field reach the Earth, saturating the ionosphere and causing a geomagnetic storm, which changes the magnetosphere and the ionosphere normal conditions. The effect is more intense in the equatorial regions and above 10 MHz, lasting hours (medium latitudes) or even 10-20 days (high latitudes). The geomagnetic storms are more frequent during periods of high solar activity, mostly after coronal mass ejections (CME). The radio waves of some frequencies may be subject to high absorption levels, causing fast fading events and uncommon radio paths.

There are two possibilities regarding radiocommunications: negative MUF variations (closing the higher bands in HF) and positive MUF variations (causing range extension in VHF). In addition to this, the HF absorption levels are higher, above all in the lower bands, so both events may cause a complete fadeout in HF. In case of a geomagnetic storm, please check the HF Absorption Levels and the foF2 variations due to geomagnetic activity. If you are a user of NVIS communications, it is interesting to check also the last available Ionograms.

 

Geomagnetic Storms


Kp Index

The geomagnetic field (the Earth's magnetic field) is perturbed due to its interaction with the Sun's Interplanetary Magnetic Field (IMF). Those perturbations can be measured using magnetometers, installed all along the Earth, wich offer the 'K indices' as a result of their measurements. The combination of the K indices measured by different magnetometers every 3 hours results in the 'Kp planetary index', which is represented in the following plot from NOAA.



No Data

Kp planetary index in the last 2 days and 1-day forecast - Updated every 15 minutes
Source: NOAA/SWPC

The following table shows the relationship between the Kp index, the Ap index (see next section) and the NOAA G-Scales. A brief description of each level is provided.


Kp Ap NOAA Status
Kp = 0 0 No storm Inactive geomagnetic field
Kp = 1 3 No storm Very quiet geomagnetic field
Kp = 2 7 No storm Quiet geomagnetic field
Kp = 3 15 No storm Unsettled geomagnetic field
Kp = 4 27 No storm Active geomagnetic field
Kp = 5 48 G1 Minor geomagnetic storm
Kp = 6 80 G2 Major geomagnetic storm
Kp = 7 140 G3 Severe geomagnetic storm
Kp = 8 240 G4 Very severe geomagnetic storm
Kp = 9 400 G5 Extremely severe geomagnetic storm

 

 

 

 

Geomagnetic Storms


Ap Index

The geomagnetic field perturbations can be measured also using a similar parameter known as Ap planetary index. The following graph shows the near-real-time Ap planetary index computed by the Australian Government IPS Radio and Space Services:

 

No Data

Ap planetary index in the last month - Updated every 24 hours
Source: IPS


The following table shows the meaning of the values:


Ap Status
0 < Ap < 30 Quiet geomagnetic field
30 < Ap < 50 Minor geomagnetic storm
50 < Ap < 100 Major geomagnetic storm
Ap > 100 Severe geomagnetic storm

 


 

 



Ionosphere status

Grade of ionization (TEC Maps)

 

Grade of Ionization (TEC Maps)

The Total Electron Content (TEC) gives an idea about the ionization grade of the ionosphere. Its unit of measurement is the TECU (1 TECU = 10E+16 electrons per square meter). The zones with the highest TEC are affected by the occurence of different ionization phenomena, such as photoionization, absorption, etc.

 

 

No Data

Wold Total Electron Content (TEC) Map - Updated every 60 min
Source: IPS (IRI-90 ionospheric model)

 

Link to the TEC global map - Updated every 5 min.
Source: Jet Propulsion Laboratory (JPL)

 

No Data

Current TEC over Europe - Updated every 5 minutes
Source: SWACI


No Data

Worldwide one hour total electron content (TEC) forecast - Updated every 5 minutes
Source: SWACI


The maps are colored by total electron content. The warmest colors show the higher TEC values, i.e. within regions of direct solar incidence (photoionization). As a general rule, the F2 layer cut frequency (foF2) will be higher with a great TEC. This way, those maps can give an idea of the hours of the day in which  the foF2 is expected to be low or high. The maps are derived from measurements of the carriers of the GPS.

 


 

 



Radiocommunications

Spectrum Monitors | HF Absorption | Ionograms | foF2 | foF2 Variations | MUF(3000)
MUF Calculators | Grey Line | HF Optimal Working Frequencies

N/A HF Radio Fadeout Level (Current)
N/A HF Radio Fadeout Level (Past 24 hours)

NOAA Alerts about HF Radio Fadeouts
Source: NOAA/SWPC
NOAA Scale (pdf)

 

Sin datos

Sin datos
HF Comms Warning
Sin datos
Current HF Fadeout
Sin datos
HF Fadeout Warning
Sin datos
Polar Absorption (PCA)

IPS Alerts about HF Communications
Source: IPS

 

Radiocommunications


Spectrum Monitors

During a solar flare event, intense electromagnetic radiation in the X-Rays band and the radio bands is emitted from the Sun. When this radiation reaches the Earth, a noise storm may occur, making worse the signal-to-noise ratio in radiocommunication systems working in the HF, VHF and UHF bands. The noise storms usually last from minutes up to one hour, although a chain of events may last even more. The spectrum monitors allow us to analyze the intensity of the radio signals received in a particular radiocommunications band, showing the results in graphical diagrams. Those measurements provide an idea of the better working frequencies for each hour of the day.

 

No Data

Culgoora Spectrograph (Australia). 18-1800 MHz.
Source: IPS

 

No Data

Hiraiso Spectrograph (Japan). 25-2500 MHz.
Source: NICT/Hiraiso Solar Observatory

 

Sin datos

Link to the Calisto Spectrograph in Humain (Belgium). 45-387,6 MHz
Source: SIDC

 

The images show several spectrum monitors in the VHF and UHF bands, placed in Australia, Japan and Belgium. Please take into account that noise storms affect the sunlit areas of the Earth (day), so during the local night those instruments do not detect any storm. During a solar flare, check the sunlit areas using the Grey Line map.

 

 

Radiocommunications


HF Absorption

During or after a solar flare, the X-ray emissions, the solar radiation storms and the geomagnetic storms may cause a rise of the grade of ionization in the D-layer of the ionosphere, increasing the absorption of the radio waves travelling through this layer up to levels that may be of importance. As a result, fading in the HF radio links may occur, especially in the lower frequencies of the band.

 

No Data

Current HF fadeout - Updated every 5 minutes
Source: IPS


No Data

Last HF fadeout event (check the date) - Updated in accordance with solar activity
Source: IPS

The maps show the Absorption Limited Frequency (ALF), that is, the minimum frequency able to propagate along about 1500 km paths during absorption events.  To interpret the map during one of those events, estimate the first reflection point in the ionosphere for the working path and identify the ALF using the contour lines. If the frequency of operation is lower than this estimated ALF, it is most probably that the radio link will not work. Using a frequency of operation (if possible, depending on the MUF) higher than the ALF increases the probability of establising the radio link. The first map shows real time data and the second map shows the ALF during the last important event (check the date).

 

No Data

Global D-region absorption prediction - Highest affected frequency by 1 dB absorption
Source: NOAA/SWPC - DRAP2

 

No Data

Highest affected frequency by 10 dB absorption
North Pole radio paths
Source: NOAA/SWPC - DRAP2

No Data

Highest affected frequency by 10 dB absorption
South Pole radio paths
Source: NOAA/SWPC - DRAP2

 

Tabular values of the current highest affected frequency (HAF) by 1 dB absorption for every location in the world (NOAA/SWPC)


The maps provided by NOAA show the highest affected frequency (HAF) by 1 dB absoprtion (world map) or 10 dB (polar area maps), for vertical radio paths. Radio links working in frequencies lower than the HAF will be affected by higher absorption values In the world map, the attenuation bar graph on the right-hand side of the graphic displays the expected attenuation in dB as a function of frequency for vertical radio wave propagation at the point of maximum absorption on the globe. This graph is only valid at this point. In order to compute the resulting total approximate absorption for HF circuits in other areas and frequencies, please use the following procedure:
1) Make an estimate of the coordinates of the first point of ionospheric reflection for your HF circuit.
2) Check the NOAA DRAP2 tabular values and pick the HAF for this point. At this frequency, the absorption level is:

A(HAF) = 1 dB.

3) Compute the absorption for your frequency of operation "F", using the following formula:

A(Fver) = (HAF/F)^(3/2) x A(HAF) = (HAF/F)^(3/2) dB

4) If "T" is the takeoff angle of your antenna, the absorption for the corresponding oblique path at the same point is:

A(Fob) = A(Fver)/sin(T) dB

5) Repeat the procedure for all ionospheric reflections in the radio path and finally add up all the computed absorptions.

 

Sin datos

D-Region global absorption prediction at 5 MHz
Source: NOAA/SWPC - DRAP2
Sin datos

D-Region global absorption prediction at 10 MHz
Source: NOAA/SWPC - DRAP2

Sin datos


D-Region global absorption prediction at 15 MHz
Source: NOAA/SWPC - DRAP2

Sin datos


D-Region global absorption prediction at 20 MHz
Source: NOAA/SWPC - DRAP2

Sin datos


D-Region global absorption prediction at 25 MHz
Source: NOAA/SWPC - DRAP2

Sin datos

D-Region global absorption prediction at 30 MHz
Source: NOAA/SWPC - DRAP2

 

The six maps shown above are provided by NOAA and show the global ionospheric D-Region absorption prediction at 5, 10, 15, 20, 25 and 30 MHz for vertical radio paths (NVIS). If "T" is the takeoff angle of your antenna, the absorption for the corresponding oblique path at the same point is:

A(Fob) = A(Fver)/sin(T) dB

Being A(Fver) the absorption observed in the map for the vertical radio path and A(Fob) the absorption calculated for the oblique path. Please take into account that each map is valid only for the specified frequency.

 

No Data

Current absorption (dB) at 5 MHz

No Data

Current absorption (dB) at 10 MHz

No Data

Current absorption (dB) at 15 MHz

No Data

Current absorption (dB) at 20 MHz

No Data

Current absorption (dB) at 25 MHz


No Data

Current absorption (dB) at30 MHz


Current absorption (dB) maps at 5, 10, 15, 20, 25 and 30 MHz - Updated every 5 minutes
Source: Solar Terrestrial Dispatch


Each map shows the current absorption levels (dB) in the indicated frequency (5, 10, 15, 20, 25 and 30 MHz).

 

 

 

Radiocommunications


Ionograms

If the radio wave reaches the ionosphere following a vertical o near vertical path (NVIS), reflection will occur in the F2 layer only if the frequency of operation is below a threshold known as F2 layer critical or cut frequency (foF2), which can be measured using ionosondes. Two inonosondes provide public data in Spain: The Ebro Observatory (Roquetes, Tarragona, NE) and the National Institute for Aerospace Technology (El Arenosillo, Huelva, SW). The corresponding latest ionograms are shown. If you look for data from other ionosondes around the world, please see the world map below.

 

No Data

Latest ionogram from the Roquetes Station (Tarragona, Spain) - Updated every 2 minutes.
Source: Ebre Observatory


No Data

Latest ionogram from the El Arenosillo Station (Huelva, Spain) - Updated every 15 minutes.
Source: Spanish National Institute for Aerospace Technology (INTA)

The intepretation of all the data collected by an ionosonde is a quite difficult process. Frequency (MHz) is represented on the X-axis and the virtual height (km) on the Y-axis. If the ionosonde detects ionospheric reflection for a particular frequency, a point is drawn on the coordinates corresponding to that frequency and virtual height. On the left side we can find derived empiric data such as the measured critical frequency foF2 (MHz) and some estimated data such as the standard MUF for radio links of 3000 km (MUF(D)). On the bottom side we can find an estimation of the MUF derived for different distances, very useful if your goal is to establish HF radio links from points near the ionosonde to other stations located at the indicated distances, using oblique paths.

 

Worldwide network of Lowell ionosondes
Source: Center for Atmospheric Research, University of Massachussets Lowell

 


Radiocommunications


foF2 Maps

If the radio wave reaches the ionosphere following a vertical o near vertical path (NVIS), reflection will occur in the F2 layer only if the frequency of operation is below a threshold known as F2 layer critical or cut frequency (foF2), which can be measured using ionosondes. The following experimental maps are built using data from ionosondes located in Australia, Japan, South Africa, Italy, Argentina and the United States.

 

No Data

Current foF2 - World Map - Updated every 1-hour intervals
Source: IPS


No Data

Current foF2 in Australasia - Updated every 1-hour intervals
Source: IPS

 

Each map shows an extrapolation of the foF2 derived for each region, using data from the nearest ionosondes. Those values can be used as MUF thresholds for NVIS (Near Vertical Incident Skywave) links, that is, using an aerial system with a very high takeoff angle, being able to reach ranges of up to 500 km without shadow areas.

 

 

Radiocommunications


foF2 variations due to geomagnetic activity

When the geomagnetic activity is high, as a consequence of geomagnetic storms started by solar flares or coronal mass ejections (CME), the F2 layer cut frequency foF2 may suffer important variations which could affect the HF radio links, both NVIS and long-distance. A geomagnetic storm may cause the ionosphere's grade of ionization to be increased (higher foF2 and MUFs) or diminished (lower foF2 and MUFs).

 

No Data

STORM Time Empirical Ionospheric Correction Model
Source: NOAA/SWPC

 

This NOAA/SWPC graph shows the F region critical frequency (foF2) scaling factor, to be applied to the foF2 mean value in real-time during a geomagnetic storm. This graph provides an idea of the influence of a geomagnetic storm on the foF2 and the MUF. There are separate graphs for the Northern and Southern Hemispheres and for three latitude areas: 30º, 50º and 70º. Values equal to 1 are an indicator of normal conditions, that is, it is not necessary to apply corrections to the foF2 values. In order to get the exat value of foF2 in real time, check the ionograms available in this panel.

 


Radiocommunications


MUF(3000)

The URSI defines the MUF as "the maximum frequency for inospheric transmission using an oblique path, for a given system". Using oblique paths, we will have a different MUF for each link distance. The following map shows MUF data for radio links larger than 3000 km.

 

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Near-real-time MUF(3000) global map - Updated every 5 minutes
Source: Solar Terrestrial Dispatch

 

Click here to know how to use this map.

 

 

 

 

Radiocommunications


Online MUF Calculators

Free online software available on the Internet for MUF calculations using a variety of parameters.

VOACAP Online
voacap.com

 

Prediction Online Tools
IPS Radio and Space Services

 

MUF Calculation for Radio Links
ESA/AMSAT - Proyecto Ionosfera

K1TTT MOF/LOF Propagation Program
David R Robbins (K1TTT)

 

 


Radiocommunications


Grey Line

The grey line is the da/night terminator line over the Earth. The D Region in the ionosphere (where HF signals absorption occurs) quickly disappears in the dark side of the grey line, rising again in the opposite side. Propagation conditions will be enhanced for radio paths following the grey line.

 

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Grey Line - Please reload the page to update the image
Source: Fourmilab Switzerland

The figure shows the position of the grey line (day/night terminator) in the world map. This map is also interesting to identify the geographical areas potentially affected by solar events hitting the day area of the Earth, such as the radio fadeouts caused by X-Ray emissions, or the noise storms, which can be analyzed with the help of spectrum monitors.

 

 

 

 

Radiocommunications


HF Optimal Working Frequencies

Current optimal working frequencies for global radio links. Reliable during 80% of time of the corresponding month, unless there is an occurrence of events related to space weather: radio fadeouts, solar radiation storms and geomagnetic storms.

USA Oeste USA Central USA Este Sudamérica Norte Sudamérica Central Sudamérica Sur Europa Occidental Europa Oriental Japón Australia India

Optimal Working Frequencies for each geographic area
Source: Propagation Resource Center - NW7US (HFRadio.org)

Select the region where your HF transmitter is located. You will get a table with the optimal working frequencies to establish radio links with all the other areas.


Conditions in the 160m band for medium and high latitude radio paths in the Northern Hemisphere
Source: Solar Terrestrial Dispatch

 


 

 



Aurora

Aurora oval | Aurora Forecasts

Aurorae borealis occur during episodes upon which the interplanetary magnetic field (IMF) module is powerful enough and its Bz component points southwards when reaching the Earth. The solar wind reaches the polar areas and collides with the atoms and molecules of the upper layers of the atmosphere, causing the emission of radiation at different wavelengths (colors). Aurorae borealis activity causes the electric currents within the ionosphere to increase, making higher the probability of fading in the radio paths crossing the aurora due to absorption, especially in the 160 meters HF band.

 

Aurora oval

 

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Auroral oval in the North Pole
Source: NOAA/POES


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Auroral oval in the South Pole
Source: NOAA/POES

The plots show the current extent and position of the auroral oval at each pole, extrapolated from measurements taken during the most recent polar pass of the NOAA POES satellite. The aurora oval is an elliptical band around each geomagnetic pole ranging from about 75 degrees magnetic latitude at local noon to about 67 degrees magnetic latitude at midnight under average conditions. Those locations experience the maximum occurrence of aurorae.  The aurora widens to both higher and lower latitudes during the expansion phase of a magnetic substorm.

 


Aurorae


Aurora Forecasts

Aurorae borealis occur during episodes upon which the interplanetary magnetic field (IMF) module is powerful enough and its Bz component points southwards when reaching the Earth. The solar wind reaches the polar areas and collides with the atoms and molecules of the upper layers of the atmosphere, causing the emission of radiation at different wavelengths (colors).


Aurora Ovation North

Latest Aurora Borealis forecast (North Pole)
Source: OVATION Auroral Forecast (NOAA)


Aurora Ovation South

Latest Aurora Australis forecast (South Pole)
Source: OVATION Auroral Forecast (NOAA)

 

 

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Visible auroral activity estimation - Updated every 1 hour
Source: Solar Terrestrial Dispatch

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Latest aurora forecast - North Polar
Source: Geophysical Institute, University of Alaska Fairbanks

No Data

Latest aurora forecast - South Polar
Source: Geophysical Institute, University of Alaska Fairbanks

 


 

 



Bulletins

NASA | NOAA | ESA | IPS | RAL | Ebro | IGN | Other

 

National Aeronautics and Space Administration

Latest bulletins from the NASA (USA):

ISWA - Integrated Space Weather Analysis System.

 



Bulletins


 

National Oceanic and Atmospheric Administration

Latest bulletins from the NOAA (USA):

NOAA/SWPC - Today's Space Weather.

NOAA/SWPC - Joint USAF/NOAA 3-day Report of Solar and Geophysical Activity.

NOAA/SWPC - Space Weather Advisory Bulletin.

NOAA/SWPC - Latest Solar-Geophysical Data (SWPC Anonymous FTP Server).

NOAA/SWPC - Solar Cycle Progression.

NOAA/SWPC - Radio User's Page.

NOAA/NGDC (National Geophysical Data Center) - Solar Data Services.

NOAA/SWPC - Auroral Activity Extrapolated from NOAA POES.

NOAA/NWS - Space Weather for Aviation Service Providers.

NOAA/SWPC - Last solar radio bursts.

 

WWV Geophysical message alert, every 3 hours
Source: NOAA/NWS Space Environment Center

 



Bulletins


European Space Agency (ESA)

Latest bulletins from the European Space Agency (ESA):

ESA - Today's Space Weather.

ESA/AMSAT - Ionosphere Project - MUF Calculation for Radio Links.

ESA/BAE Systems - Daily Ionospheric Forecasting Service (DIFs).

 

 


Bulletins


IPS Radio and Space Services

IPS: Global HF propagation.

IPS: Recent Flare and Fadeout Information (Larger than C8 Only) .

IPS: Solar Conditions Summary and Forecast.

 


 

Bulletins


Rutherford Appleton Laboratory

RCRU/Rutherford Appleton Laboratory - Short Term Ionospheric Forecast (STIF).

 

 


Boletines Informativos


Ebro Observatory

Observatorio del Ebro

Solar Data (Monthly Mean Wolf Number).

Preliminary Magnetograms - Horta S. Joan Variometric Station.

 

 

Bulletins


Instituto Geográfico Nacional (IGN)

IGN

Latest magnetogram and K index preliminary values. San Pablo Observatory (Toledo, Spain).

Most significative geomagnetic storms in the last years. San Pablo and Güimar Observatories (Spain).

 

 

 

Bulletins


Other Bulletins

SOLAR ACTIVITY

NASA - Current images of the Sun (SDO/AIA).

Big Bear Solar Observatory - (New Jersey Institute of Technology) - Solar Activity Report.

GEOMAGNETISM

Real Time Dst Estimate (Berkeley University).

USGS - National Geomagnetism Program - Real time geomagnetic data.

AURORAE

STD - Hourly STD DMSP/POLAR Auroral Activity Report.

AuroraWatch.

John Hopkins University - Latest auroral data.

GREY LINE

Dx.qsl.net - Grey Line Map.

Worldtime.com - Grey Line.

RF PROPAGATION

ARRL - Propagation of RF Signals.

DX World.net - Solar & Propagation News.

Dx.qsl.net - Propagation.

Monthly Propagation Forecasts by EA3EPH (Alonso Mostazo).

THUNDERSTORMS

AEMET (Spanish National Meteorological Agency) - Latest 6-hours lightning map (Spain).

 


 

 



Links

Prediction Centers | Research and Education | Civil Protection | Amateur Radio | Spanish Government

 

Prediction and Observation Centers


European Space Weather Portal
European Space Agency (ESA)

Space Weather Prediction Center (SWPC)
NOAA (USA)


Space Weather Web
Laboratorio Rutherford Appleton (UK)


IPS Radio and Space Services
Australian Government


Observatorio del Ebro

Ebro Observatory
Spain

CNIG-IGN

CNIG - Geomagnetism
Instituto Geográfico Nacional (Spain)



 

 

Links


Research and Education

European Space Weather Portal
COST 724 (Europe)

Space Weather Prediction Center (SWPC)
NOAA (USA)



International Space Environment Services (ISES)
FAGS


National Geophysical Data Center (NGDC)
NOAA (USA)


National Space Weather Program (NSWP)
Interagency program (USA)


Space Weather Journal
American Geophysical Union (USA)


Space Weather Center
Space Science Institute (USA)


SWENET - Space Weather European Networkl
European Space Agency (ESA)


Propagation Studies Committee
Radio Society of Great Britain (UK)


Very Low Frequency (VLF) Group
Stanford University (USA)

 

 

 

 

Links


Civil Protection (Spain)

General Directorate of Civil Protection and Emergencies (DGPCE, Spain)

Emergency Radio Network (REMER, Spain)

 


 

Links


Amateur Radio Service

IARU Región I Bandplan (pdf)

IARU Región II Bandplan

IARU Region III Bandplan (doc)

 


 

Links


Spanish Government

National Frequency Allocation Plan (CNAF)

 


 

 



Remarks

The goal of this page is to offer real-time information of interest for the Radio HF band users.

This is a non-official page.

All images displayed are property of their respective authors. The source is shown below every image.

Please check the date of publication of each image for validation purposes.

You can find a brief description of every image on the paragraphs marked as ""

You can find how to interpret the data on the paragraphs marked as ""

If you need further detailed information regarding each data, refer to the tutorial (in Spanish) clicking "".

For any questions or comments, please contact me using this form.

 


 

 


 

 

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Page last updated: 13 MAY 2014.

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