Observations of conduction driven evaporation in the early rise phase of solar flares
Observations of conduction driven evaporation in the early rise phase of solar flares
复制标题
太阳耀斑早期上升阶段传导驱动蒸发的观测
DOI：
10.1051/0004-6361/200811196
复制
发表时间：
2009
影响因子：
6.5
通讯作者：
Battaglia M
中科院分区：
文献类型：
--
作者：
Battaglia M
背景经典的耀斑图片描绘了一束电子，这些电子在日冕的某个位置加速，撞击色球层。电子在致密色球等离子体中停止，以硬 X 射线形式发射轫致辐射。周围的材料被沉积的能量加热并膨胀到磁耀斑环中，这一过程称为色球蒸发。在这种观点中，色球层的硬 X 射线发射被耀斑环路中的热等离子体的软 X 射线发射所取代，软 X 射线发射是非热粒子束撞击的直接结果。然而，存在对事件的观察，其中在硬X射线发射开始前几分钟观察到软X射线发射的显着增加。这种前耀斑发射显然与经典耀斑图像相矛盾。目的首次对此类太阳耀斑的前耀斑阶段进行详细研究。目的是了解这些事件的早期上升阶段。我们希望通过热传导等替代能量传输机制来解释观测到的发射的时间演变。方法通过成像和光谱分析显示明显的前耀斑发射的RHESSI事件。研究了图像和全太阳光谱的时间演化，并将其与传导驱动色球蒸发的理论预期进行了比较。结果前耀斑阶段的特征是来自日冕源的纯热发射，发射测量和密度不断增加。在这个最早的阶段之后，光谱中出现了一条通往更高能量的小非热尾，并且变得越来越明显。然而，图像仍然只显示一个 X 射线源，这意味着这种非热发射是日冕的。发射量和密度的增加表明材料被添加到日冕区域。最合理的来源是色球层蒸发的物质。热通量提供的能量能够驱动色球蒸发。我们表明，经常使用的经典斯皮策处理导电通量是不适用的。导电通量饱和。在预耀斑阶段，日冕源的温度保持恒定或升高。日冕中的持续加热对于解释这一观测结果是必要的。结论四次太阳耀斑预耀斑阶段的观测结果与饱和热通量驱动的色球蒸发一致。此外，需要在电晕中持续加热以维持观察到的温度。
ContextThe classical flare picture features a beam of electrons, which were accelerated in a site in the corona, hitting the chromosphere. The electrons are stopped in the dense chromospheric plasma, emitting bremsstrahlung in hard X-rays. The ambient material is heated by the deposited energy and expands into the magnetic flare loops, a process termed chromospheric evaporation. In this view hard X-ray emission from the chromosphere is succeeded by soft-X-ray emission from the hot plasma in the flare loop, the soft X-ray emission being a direct consequence of the impact of the non-thermal particle beam. However, observations of events exist in which a pronounced increase in soft X-ray emission is observed minutes before the onset of the hard X-ray emission. Such pre-flare emission clearly contradicts the classical flare picture.AimsFor the first time, the pre-flare phase of such solar flares is studied in detail. The aim is to understand the early rise phase of these events. We want to explain the time evolution of the observed emission by means of alternative energy transport mechanisms such as heat conduction.MethodsRHESSI events displaying pronounced pre-flare emission were analyzed in imaging and spectroscopy. The time evolution of images and full sun spectra was investigated and compared to the theoretical expectations from conduction driven chromospheric evaporation.ResultsThe pre-flare phase is characterized by purely thermal emission from a coronal source with increasing emission measure and density. After this earliest phase, a small non-thermal tail to higher energies appears in the spectra, becoming more and more pronounced. However, images still only display one X-ray source, implying that this non-thermal emission is coronal. The increase of emission measure and density indicates that material is added to the coronal region. The most plausible origin is evaporated material from the chromosphere. Energy provided by a heat flux is capable of driving chromospheric evaporation. We show that the often used classical Spitzer treatment of the conductive flux is not applicable. The conductive flux is saturated. During the preflare-phase, the temperature of the coronal source remains constant or increases. Continuous heating in the corona is necessary to explain this observation.ConclusionsThe observations of the pre-flare phase of four solar flares are consistent with chromospheric evaporation driven by a saturated heat flux. Additionally, continuous heating in the corona is necessary to sustain the observed temperature.
登录
查看更多内容
太阳耀斑的光束驱动色球蒸发模型 - 该模型不受非脉冲大型耀斑观测结果的支持
DOI：
--
发表时间：
1990
期刊：
影响因子：
--
作者：
U. Feldman
通讯作者：
U. Feldman
影响因子：
2.8
作者：
J. Culhane;E. Hiei;G. Doschek;A. M. Cruise;Y. Ogawara;Y. Uchida;R. Bentley;C. M. Brown;J. Lang;T. Watanabe;J. Bowles;R. Deslattes;U. Feldman;A. Fludra;P. Guttridge;A. Henins;J. Lapington;J. Magraw;J. Mariska;J. Payne;K. Phillips;P. Sheather;K. Slater;K. Tanaka;E. Towndrow;M. Trow;A. Yamaguchi
通讯作者：
J. Culhane;E. Hiei;G. Doschek;A. M. Cruise;Y. Ogawara;Y. Uchida;R. Bentley;C. M. Brown;J. Lang;T. Watanabe;J. Bowles;R. Deslattes;U. Feldman;A. Fludra;P. Guttridge;A. Henins;J. Lapington;J. Magraw;J. Mariska;J. Payne;K. Phillips;P. Sheather;K. Slater;K. Tanaka;E. Towndrow;M. Trow;A. Yamaguchi
太阳耀斑中的非局域热传输
DOI：
10.1086/165608
发表时间：
1986
期刊：
The Astrophysical Journal
影响因子：
--
作者：
J. Karpen;C. DeVore
通讯作者：
C. DeVore
激光加热等离子体中大温度梯度引起的离子声湍流和热导率降低的测量
DOI：
--
发表时间：
1980
期刊：
影响因子：
--
作者：
D. R. Gray;J. Kilkenny
通讯作者：
J. Kilkenny