### 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 [E_{th}], each event is divided into three phases during the nonthermal-energy input[dE_{nth}/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.

Original language | English (US) |
---|---|

Pages (from-to) | 329-344 |

Number of pages | 16 |

Journal | Solar Physics |

Volume | 264 |

Issue number | 2 |

DOIs | |

State | Published - Jul 14 2010 |

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### All Science Journal Classification (ASJC) codes

- Astronomy and Astrophysics
- Space and Planetary Science

### Keywords

- Flares
- Hard
- X-ray bursts

### Cite this

*Solar Physics*,

*264*(2), 329-344. https://doi.org/10.1007/s11207-010-9589-1

}

*Solar Physics*, vol. 264, no. 2, pp. 329-344. https://doi.org/10.1007/s11207-010-9589-1

**Investigation of the Neupert effect in the various intervals of solar flares.** / Ning, Zongjun; Cao, Wenda.

Research output: Contribution to journal › Article

TY - JOUR

T1 - Investigation of the Neupert effect in the various intervals of solar flares

AU - Ning, Zongjun

AU - Cao, Wenda

PY - 2010/7/14

Y1 - 2010/7/14

N2 - 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.

AB - 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.

KW - Flares

KW - Hard

KW - X-ray bursts

UR - http://www.scopus.com/inward/record.url?scp=77954761750&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=77954761750&partnerID=8YFLogxK

U2 - https://doi.org/10.1007/s11207-010-9589-1

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

M3 - Article

VL - 264

SP - 329

EP - 344

JO - Solar Physics

JF - Solar Physics

SN - 0038-0938

IS - 2

ER -