Testing the Neupert Effect

Turbulence in Space Plasmas

“…The time history of the integrated non-thermal X-ray flux roughly corresponds to the time profile of the thermal X-ray emission (this is called Neupert effect: see [161] for recent results). So the larger the non-thermal X-ray flux, the more the heating expected.…”

The Sun as a Stellar Laboratory: Unsolved Problems

“…This situation would be highly unstable to wave generation and dissipate the beam, unless large pitch angles reduced the beam current or the beam flowed in very hot narrow channels within the area. Based on the smallest HXR source areas observed by RHESSI, Veronig et al (2003) found that the situation is very close to the electron thermal speed limit, but not over it, again depending on the value of spectral cut off E c . Consequently, return current instability may, as suggested by Brown & Melrose (1977) be acting to limit the accelerated electron flux.…”

“…In fact it might only indicate a degree of synchronism between the electron acceleration process and a quite distinct plasma heating process, each associated with reconnection , with no direct heating by the beam. To check this, Veronig et al (2003) have used RHESSI and GOES data to infer the actual total electron beam power Pe(t) time variation (which depends on HXR flux, spectral index and E c) and total power Pin(t) into the hot plasma required to drive the observed variations in its temperature and emission measure and to offset radiative and conductive losses. Physically, if electrons heat the plasma one would expect a much better cross correlation of P; (t) and Pin(t) than of the diagnostic HXR and SXR light curves.…”

Ramaty High Energy Solar Spectroscopic Imager (RHESSI)

“…For flare hard X-ray spectra with a flattening at low energies, the derived electron source spectra appear to show a roll-off around 20 -40 keV Kašparová et al (2005), but after correcting for albedo (the Compton scattering of the source hard X-rays by the solar photosphere), using a newly-developed Green's function method Kontar et al (2006), all the derived source electron power-law spectra extend with no roll-off down to ≤20 keV and sometimes as low as ∼12 keV (see also Massone et al (2004), Sui et al (2005Sui et al ( , 2007), where the hot flare thermal emission dominates. These spectral measurements have also been used to demonstrate the so-called Neupert Effect, in which the time history of the thermal soft X-ray emission in many flares closely matches the time integral of the non-thermal hard X-ray emission Veronig et al (2005).…”