Springer Nature is making SARS-CoV-2 and COVID-19 research free. View research | View latest news | Sign up for updates

The RHESSI Microflare Height Distribution

  • 84 Accesses

  • 5 Citations


We present the first in-depth statistical survey of flare source heights observed by RHESSI. Flares were found using a flare-finding algorithm designed to search the 6 – 10 keV count-rate when RHESSI’s full sensitivity was available in order to find the smallest events (Christe et al. in Astrophys. J. 677, 1385, 2008). Between March 2002 and March 2007, a total of 25 006 events were found. Source locations were determined in the 4 – 10 keV, 10 – 15 keV, and 15 – 30 keV energy ranges for each event. In order to extract the height distribution from the observed projected source positions, a forward-fit model was developed with an assumed source height distribution where height is measured from the photosphere. We find that the best flare height distribution is given by g(h)∝exp (−h/λ) where λ=6.1±0.3 Mm is the scale height. A power-law height distribution with a negative power-law index, γ=3.1±0.1 is also consistent with the data. Interpreted as thermal loop-top sources, these heights are compared to loops generated by a potential-field model (PFSS). The measured flare heights distribution are found to be much steeper than the potential-field loop height distribution, which may be a signature of the flare energization process.

This is a preview of subscription content, log in to check access.


  1. Altschuler, M.D., Newkirk, G.: 1969, Solar Phys. 9, 131.

  2. Aschwanden, M.J., Schwartz, R.A., Alt, D.M.: 1995, Astrophys. J. 447, 923.

  3. Aschwanden, M.J., Brown, J.C., Kontar, E.P.: 2002, Solar Phys. 210, 383.

  4. Catalano, C.P., van Allen, J.A.: 1973, Astrophys. J. 185, 335.

  5. Christe, S., Hannah, I.G., Krucker, S., McTiernan, J., Lin, R.P.: 2008, Astrophys. J. 677, 1385.

  6. Hannah, I.G., Christe, S., Krucker, S., Hurford, G.J., Hudson, H.S., Lin, R.P.: 2008, Astrophys. J. 677, 704.

  7. Hoeksema, J.T.: 1984, Structure and evolution of the large scale solar and heliospheric magnetic fields. PhD thesis, Stanford Univ., CA.

  8. Hurford, G.J., Schmahl, E.J., Schwartz, R.A., Conway, A.J., Aschwanden, M.J., Csillaghy, A., Dennis, B.R., Johns-Krull, C., Krucker, S., Lin, R.P., McTiernan, J., Metcalf, T.R., Sato, J., Smith, D.M.: 2002, Solar Phys. 210, 61.

  9. Kane, S.R.: 1983, Solar Phys. 86, 355.

  10. Kane, S.R., Anderson, K.A., Evans, W.D., Klebesadel, R.W., Laros, J.: 1979, Astrophys. J. Lett. 233, 151.

  11. Kontar, E.P., Hannah, I.G., MacKinnon, A.L.: 2008, Astron. Astrophys. 489, 57.

  12. Kontar, E.P., Hannah, I.G., Jeffrey, N.L.S., Battaglia, M.: 2010, Astrophys. J. 717, 250.

  13. Matsushita, K., Masuda, S., Kosugi, T., Inda, M., Yaji, K.: 1992, Publ. Astron. Soc. Japan 44, 89.

  14. Ohki, K., Takakura, T., Tsuneta, S., Nitta, N.: 1983, Solar Phys. 86, 301.

  15. Sato, J., Matsumoto, Y., Yoshimura, K., Kubo, S., Kotoku, J., Masuda, S., Sawa, M., Suga, K., Yoshimori, M., Kosugi, T., Watanabe, T.: 2006, Solar Phys. 236, 351.

  16. Schatten, K.H., Wilcox, J.M., Ness, N.F.: 1969, Solar Phys. 6, 442.

  17. Schrijver, C.J., De Rosa, M.L.: 2003, Solar Phys. 212, 165.

  18. Smith, D.M., Lin, R.P., Turin, P., Curtis, D.W., Primbsch, J.H., Campbell, R.D., Abiad, R., Schroeder, P., Cork, C.P., Hull, E.L., Landis, D.A., Madden, N.W., Malone, D., Pehl, R.H., Raudorf, T., Sangsingkeow, P., Boyle, R., Banks, I.S., Shirey, K., Schwartz, R.: 2002, Solar Phys. 210, 33.

  19. Takakura, T., Tanaka, K., Nitta, N., Kai, K., Ohki, K.: 1986, Solar Phys. 107, 109.

  20. Tsuneta, S., Takakura, T., Nitta, N., Makishima, K., Murakami, T., Oda, M., Ogawara, Y., Kondo, I., Ohki, K., Tanaka, K.: 1984, Astrophys. J. 280, 887.

  21. Wang, Y., Sheeley, N.R. Jr.: 1992, Astrophys. J. 392, 310.

Download references

Author information

Correspondence to S. Christe.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Christe, S., Krucker, S. & Saint-Hilaire, P. The RHESSI Microflare Height Distribution. Sol Phys 270, 493–502 (2011). https://doi.org/10.1007/s11207-011-9777-7

Download citation


  • Solar Phys
  • Scale Height
  • Height Distribution
  • Magnetic Loop
  • Spin Axis