Solar

Current Conditions

The following links together provide a comprehensive review of the current state of our local star:

SpaceWeather.com - easy to understand. Good references to some of the key terms

Solar Terrestrial Dispatch - a great summary site. Rollover graphs for the past 24hrs.

Today's Space Weather - The definative site from the Space Environment Centre (where most of the other sites get their data)

Solar Conditions - From Australia's own IPS Radio and Space Services. Spectrographs and magnetograms (via 'Solar Images')

Solar Maps - Nice Earthside and farside graphs from Raben Systems.

 

Introduction

From about 40km to 200km above the surface of the Earth is a layer of the atmosphere known as the Ionosphere. At this high altitude the atmosphere is bombarded with incoming solar radiation. The collisions between the particles that make up this radiation (mostly electrons but some protons too) knock the electrons free from the atoms in the atmosphere. This creates electrically charged ions (hence the ionosphere name).

The variation in the incoming solar radiation (often refered to as the solar weather) causes the level of ionisation to fluctuate. This is known as scintillation. The same name applies to the movement of air pockets in the low atmosphere that makes stars "twinkle" or makes a hot bitumen road appear to shimmer.

A Sudden Ionospheric Distrubance (SID) is where a sudden burst of incoming solar radiation from a flare dramatically increases the ionisation of the ionosphere (D layer), making it more opaque.

Here's an example from Simple:

A typical daily radio profile but note the sudden drop around 9:30 LST from an SID

The amount of radiation from space making it through the atmosphere to Simple's antennas suddenly dropped as the SID suddenly increased the amount of ionisation. The ionosphere then slowly recovers back to the normal level over the following 2 hours.

 

This is a great example of solar continuum storming, where the sun becomes a bright radio emitter for many hours or even days, usually associated with a large and complex sunspot group.

The graph shows Australian Eastern Summer Time (UT+11) on the 5th of March 2004. The top panel - the power detected by each of the receivers - shows that the Galactic background looks normal up until about 8 or 9am when the sun starts creeping into Simple's beam pattern. The sun was bubbling and boiling away all day until it left the antennas beam pattern at about 6 or 7pm. Around 8 and 9pm is some terrestrial interference not associated with the sun.

The bottom panel shows the interferometer output over the day. In the early morning hours before sun rise are the normal fringes we observe for Centaurus-A and the Galaxy. They are dwarved by the scale of the solar fringes through the day! This textbook perfect solar interference fringe pattern is the kind of thing that really gets we backyard interferometer types buzzing :-) Notice that the RFI later in the day does not have the interference fringes characteristic of an astronomical source.

Often one of the hardest things about RA is figuring out what it was you've captured and whether anyone else "saw" the same thing! This is where you fellow RAer's come in handy. Here's an exchange between John "Dusty" Samouce in Sula, Montanna, USA and Dave Brodrick in Narrabri, NSW, Australia via the RadioJOVE email list Sunday 7/3/04:

Dusty:

Attached is the bursts that happened at 1913 and 2100 UT today.

The antenna was in S Phasing configuration when the two bursts were recorded. There were lots of small spikes and "rumblings" most of the afternoon. This and the .spd files will be added to JOVE Archive.

There have been some changes in the configuration of my "JOVE Trio" antenna system: the NE-SW set that were SE Phasing are now Anti-Phasing with the removal of the 1/4 lambda phasing cable and phase reversal of one dipole, the NW-SE set that were SW Phasing are now Anti-Phasing with the removal of the 1/4 lambda phasing cable and phase reversal of one dipole, the E-W set are still configured as S Phasing.

These changes gives me "stronger" solar reception between sunrise and about 10 AM local and from about 3 PM local to sunset.

Dave:

Hi John,
I also detected one of your bursts - the one at ~21:00 – in Narrabri, NSW, Australia.

I made up an image over the same time range as the graph you produced. There is excellent agreement between your data and ours.

Regards,
Dave

Here's the two graphs: