English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

The nanoflare-heating theory predicts steady hot plasma emission in thenon-flaring active regions. It is hard to find this emission with conventionalnon-monochromatic imagers (such as Atmospheric Imaging Assembly or X-RayTelescope), because their images contain a cool temperature background. In thiswork, we search for hot plasma in non-flaring active regions using the Mg XIIspectroheliograph onboard Complex Orbital Observations Near-Earth of Activityon the Sun (CORONAS)-F/SPectroheliographIc X-ray Imaging Telescope (SPIRIT).This instrument acquired monochromatic images of the solar corona in the Mg XII8.42 \AA line, which emits only at temperatures higher than 4 MK. The Mg XIIimages contain the signal only from hot plasma without any low-temperaturebackground. We studied the hot plasma in active regions using the SPIRIT datafrom 18-28 February 2002. During this period, the Mg XII spectroheliographworked with a 105-second cadence almost without data gaps. The hot plasma wasobserved only in the flaring active regions. We do not observe any hot plasmain non-flaring active regions. The hot plasma column emission measure in thenon-flaring active region should not exceed $3 \times 10^{24}$ cm$^{-5}$. Thehot Differential Emission Measure (DEM) is less than 0.01 % of the DEM of themain temperature component. Absence of Mg XII emission in the non-flaringactive regions can be explained by weak and frequent nanoflares (delay lessthan 500 seconds) or by very short and intense nanoflares that lead tonon-equilibrium ionization.

solar physics

Estimate of the Upper Limit on Hot Plasma Differential Emission Measure  (DEM) in Non-Flaring Active Regions and Nanoflare Frequency Based on the Mg  XII Spectroheliograph Data from CORONAS-F/SPIRIT