Subarcsecond Bright Points and Quasi-periodic Upflows Below a Quiescent Filament Observed by the IRIS

TL;DR

This study reveals subarcsecond bright points and quasi-periodic upflows in a quiescent solar filament, linking magnetic reconnection and p-mode waves to filament dynamics and mass transfer.

Contribution

It provides new observations of small-scale magnetic features and upflows in a filament channel, highlighting their role in filament mass balance and the possible influence of oscillatory magnetic reconnection.

Findings

Bright points have a spatial scale of 350-580 km and last for tens of minutes.

Upflows have velocities of 5-50 km/s and are associated with blueshifted Si IV lines.

Quasi-periodic brightenings and upflows occur with a period of 4-5 minutes.

Abstract

Using UV spectra and SJIs from the IRIS, and coronal images and magnetograms from the Solar Dynamics Observatory (SDO), we present the new features in a quiescent filament channel: subarcsecond bright points (BPs) and quasi-periodic upflows. The BPs in the TR have a spatial scale of about 350$-$580 km and lifetime of more than several tens of minutes. They are located at stronger magnetic structures in the filament channel, with magnetic flux of about 10$^{17}$$-$10$^{18}$ Mx. Quasi-periodic brightenings and upflows are observed in the BPs and the period is about 4$-$5 min. The BP and the associated jet-like upflow comprise a "tadpole-shaped" structure. The upflows move along bright filament threads and their directions are almost parallel to the spine of the filament. The upflows initiated from the BPs with opposite polarity magnetic fields have opposite directions. The velocity of the upflows in plane of sky is about 5$-$50 km s$^{-1}$. The emission line of Si IV 1402.77 {\AA} at the locations of upflows exhibits obvious blueshifts of about 5$-$30 km s$^{-1}$, and the line profile is broadened with the width of more than 20 km s$^{-1}$. The BPs seem to be the bases of filament threads and the upflows are able to convey mass for the dynamic balance of the filament. The "counter-streaming" flows in previous observations may be caused by the propagation of bi-directional upflows initiated from opposite polarity magnetic fields. We suggest that quasi-periodic brightenings of BPs and quasi-periodic upflows result from small-scale oscillatory magnetic reconnections, which are modulated by solar p-mode waves.