The energy supply to X-ray bright points

Abstract

X-ray bright points (XBPs) are usually assumed to be isolated structures in the solar atmosphere that are powered exclusively by magnetic reconnection. We analyse a large XBP that does not satisfy this assumption. The XBP is observed to be connected to an active region approximately 280 000 km away by a magnetic loop. We find that the soft X-ray intensity and thermal energy of the XBP are very sensitive to the existence of the magnetic loop. Both the intensity and energy decrease significantly at the times when the loop disappears, indicating that the loop is a medium for energy transfer from the active region to the XBP. We deduce that the mechanism for the energy transfer is most likely to be Alfven or fast-mode magnetoacoustic waves created by photospheric motions in the active region. These waves can dissipate energy at the density gradient between the XBP and the loop via phase mixing or resonant absorption.