Radio Auroras

A radio aurora starts as a huge solar flare or other ejection of plasma from the Sun. If there’s enough energy, the plasma hits the Earth’s atmosphere three days later and tracks south and north from the poles. How, is complex. Again, if there’s enough energy, the result may be plasma roaring down to Earth, splatting round the atmosphere. Continuing earthwards, the result may be a visible aurora, and more rarely, a radio aurora.

Particles from the Sun are propelled towards Earth in the solar wind. They interact with the Earth and Sun’s interplanetary magnetic field. These particles track down the field lines, entering the Earth’s atmosphere at the poles. They interact with particles in the Earth’s atmosphere. The eventual result is spinning columns of plasma that support VHF backscatter.

Radio auroras are sporadic E Region events. They don’t happen often – indeed most radio amateurs would say that they’ve never participated in an auroral event, even though they are equipped for VHF DX operation. Unlike Sporadic E activity which happens annually, radio auroras are much rarer. And yet radio auroras do have a predictability and cadence too.

An estimate of the strength of the aurora and hence how far south the radio auroral oval has sunk leads speculation about necessary beam angles. If it’s a strong aurora, beaming east from the UK will enable QSOs with northern European stations. Likewise, beaming west will enable QSOs with Greenland and Canada.

The pages at my site, Ham Radio Engineering describe radio auroras and hence indicate what’s needed to optimise operating during a radio aurora. There’s also a video that gives an excellent summary of SSB operation during a radio aurora. In this case it’s on the 6m band but it could equally be on 2m. This video then goes on to describe the technical adjustments needed to exploit the enhanced propagation of an aurora.

Doppler shift is a phenomenon whereby the received signal frequency is perceived to be changed because of movement of either the sender or receiver, or the propagating medium. The latter case where the scattering medium is moving is of specific interest in amateur radio. This causes Doppler shift in frequencies and Doppler distortion from multiple scattered paths. Doppler distortion is the signature of communications via the aurora.

Navigate to my site, Ham Radio Engineering, for a list of papers, books and the like that have informed the pages about radio auroras.

[CheckpointCharlieFoodTruck]

3:00-- anyone that with a straight face calls that signal 59 can never be trusted to give an honest signal report ever again.

When everyone gets a 59, it's the participation prize of ham radio. I think people feel like if you don't tell someone they have a 59 you're hurting their feelings. It's just the atmosphere. No feelings need to get hurt.