Investigation of the Neupert effect in the various intervals of solar flares

Document Type

Article

Publication Date

7-14-2010

Abstract

The Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) gives us a chance to investigate the theoretical Neupert effect using the correlation between the thermal-energy derivative and the nonthermal energy, or the thermal energy and the integral nonthermal energy. Based on this concept, we analyze four M-class RHESSI flares on 13 November 2003, 4 November 2004, 3 and 25 August 2005. According to the evolution of the temperature [T], emission measure [EM], and thermal energy [Eth], each event is divided into three phases during the nonthermal-energy input[dEnth/dt in the units of erg s-1]. Phase 1 is identified as the interval before the temperature maximum, while after the thermal-energy maximum is phase 3, between them is phase 2. We find that these four flares show the Neupert effect in phase 1, but not in phase 3. The Neupert effect still works well in the second phase, although the cooling becomes slightly important. We define the parameter μ in the relation of, when the cooling is ignored in phase 1. Considering the uncertainties in estimating the energy from the observations, it is not possible to precisely determine the fraction of the known energy in the nonthermal electrons transformed into the thermal energy of the hottest plasma observed by RHESSI. After a rough estimate of the flare volume and the assumption of the filling factor, we investigate the parameter μ in these four events. Its value ranges from 0.02 to 0.20, indicating that a small fraction (2%-20%) of the nonthermal energy can be efficiently transformed into thermal energy, which is traced by the soft X-ray emission, and the bulk of the energy is lost possibly due to cooling. © 2010 Springer Science+Business Media B.V.

Identifier

77954761750 (Scopus)

Publication Title

Solar Physics

External Full Text Location

https://doi.org/10.1007/s11207-010-9589-1

e-ISSN

1573093X

ISSN

00380938

First Page

329

Last Page

344

Issue

2

Volume

264

Grant

0847126

Fund Ref

National Science Foundation

This document is currently not available here.

Share

COinS