Related papers: Variation of Emission Line Width in Mid- and High-…
Understanding coronal structure and dynamics can be facilitated by analyzing green-line emission, which enables the investigation of diverse coronal structures such as coronal loops, streamers, coronal holes, and various eruptions in the…
The nonthermal broadening of spectral lines formed in the solar corona is often used to seek the evidence of Alfv\'en waves propagating in the corona. To have a better understanding of the variation of line widths at different altitudes, we…
The purpose of this paper is to analyze the variation in the line width with height in the inner corona (region above 1.1 Rsun), by using the spectral data from LASCO-C1 aboard SOHO. We used data acquired at activity minimum (August -…
The relative Doppler velocities and linewidths in a polar coronal hole and the nearby quiet-Sun region have been obtained from the {\it Solar and Heliospheric Observatory} (SOHO)/{\it Coronal Diagnostic Spectrometer} (CDS) observations…
Solar extreme-ultraviolet (EUV) lines emitted by highly charged ions have been extensively studied to discuss the issue of coronal heating and solar wind acceleration. Based on observations of the polar corona by the SUMER/SOHO…
The profiles of emission lines formed in the corona contain information on the dynamics and the heating of the hot plasma. Only recently has data with sufficiently high spectral resolution become available for investigating the details of…
We investigate off-limb active region and quiet Sun corona using spectroscopic data. Active region is clearly visible in several spectral lines formed in the temperature range of 1.1--2.8 MK. We derive electron number density using line…
Spectral line widths are often observed to be larger than can be accounted for by thermal and instrumental broadening alone. This excess broadening is a key observational constraint for both nanoflare and wave dissipation models of coronal…
Observations reveal an increase with height of the line width of several coronal spectral lines probably caused by outwardly propagating Alfv{\'e}n waves. However, the spectral line width sometimes shows a sudden decrease at a height…
We present observations of the extended solar cycle activity in white-light coronagraphs, and compare them with the more familiar features seen in the Fe XIV green-line corona. We show that the coronal activity zones seen in the emission…
Spectropolarimetric results of Fraunhofer lines between 516.3nm and 532.6nm are presented in local upper solar chromosphere, transition zone and inner corona below a height of about 0.04 solar radius above the solar limb. The data were…
Since the Lalpha rocket observations of (Gabriel, Solar Phys. 21, 392, 1971), it has been realized that the hydrogen (H) lines could be observed in the corona and offer an interesting diagnostic for the temperature, density, and radial…
The spectroscopic observations presented here were acquired during the 2017 August 21 total solar eclipse with a three-channel partially multiplexed imaging spectrometer (3PAMIS) operating at extremely high orders ($>$ 50). The 4 $R_\odot$…
Alfven waves and ion-cyclotron absorption of high-frequency waves are frequently brought into models devoted to coronal heating and fast solar-wind acceleration. Signatures of ion-cyclotron resonance have already been observed in situ in…
The daily measurements of the disc-integrated solar radio flux, observed by the Radio Solar Telescope Network (RSTN), at 245, 410, 610, 1415, 2695, 4995, and 8800 MHz during the time interval of 1989 January 1 to 2019 December 17, are used…
We have measured the widths of spectral lines from a polar coronal hole using the Extreme Ultraviolet Imaging Spectrometer onboard Hinode. Polar coronal holes are regions of open magnetic field and the source of the fast solar wind. We find…
We present a detailed analysis of oxygen ion velocity distributions in the extended solar corona, based on observations made with the Ultraviolet Coronagraph Spectrometer (UVCS) on the SOHO spacecraft. Polar coronal holes at solar minimum…
The "middle corona" is a critical transition between the highly disparate physical regimes of the lower and outer solar corona. Nonetheless, it remains poorly understood due to the difficulty of observing this faint region (1.5-3 solar…
It is generally accepted that densities of quiet sun and active region plasma are sufficiently low to justify the optically thin approximation, and it is commonly used in the analysis of line emissions from plasma in the solar corona.…
{The \ion{Na}{x} X-ray lines between 10.9 and 11.2~\AA\ have attracted little attention but are of interest since they enable an estimate of the coronal abundance of Na to be made. This is of great interest in the continuing debate on the…