Browsing Institutt for teoretisk astrofysikk by Author "Joshi, Jayant"

Now showing items 1-13 of 13

  • The cause of spatial structure in solar He i 1083 nm multiplet images 
    Leenaarts, Jorrit; Golding, Thomas Peter; Carlsson, Mats; Libbrecht, Tine; Joshi, Jayant (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2016)
    Context. The He i 1083 nm is a powerful diagnostic for inferring properties of the upper solar chromosphere, in particular for the magnetic field. The basic formation of the line in one-dimensional models is well understood, ...
  • Characterization and formation of on-disk spicules in the Ca II K and Mg II k spectral lines 
    Bose, Souvik; de Jorge Henriques, Vasco Manuel; Joshi, Jayant; Rouppe van der Voort, Luc (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2019)
    We characterize, for the first time, type-II spicules in Ca II K 3934 Å using the CHROMIS instrument at the Swedish 1 m Solar Telescope. We find that their line formation is dominated by opacity shifts with the K3 minimum ...
  • Evidence of the multi-thermal nature of spicular downflows. Impact on solar atmospheric heating 
    Bose, Souvik; Rouppe van der Voort, L. H. M.; Joshi, Jayant; henriques, vasco manuel de jorge; Nobrega-Siverio, Daniel; Martinez-Sykora, Juan; De Pontieu, Bart (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2021)
    Context. Spectroscopic observations of the emission lines formed in the solar transition region commonly show persistent downflows on the order of 10−15 km s −1 . The cause of such downflows, however, is still not fully ...
  • High-resolution observations of the solar photosphere, chromosphere, and transition region: A database of coordinated IRIS and SST observations 
    Rouppe van der Voort, Luc; De Pontieu, Bart Walter; Carlsson, Mats; de la Cruz Rodriguez, Jaime; Bose, Souvik; Chintzoglou, Georgios; Drews, Ainar; Froment, Clara; Gošić, Milan; Graham, David R.; Hansteen, Viggo; de Jorge Henriques, Vasco Manuel; Jafarzadeh, Shahin; Joshi, Jayant; Kleint, Lucia; Kohutova, Petra; Leifsen, Torben; Martinez-Sykora, Juan; Nóbrega Siverio, Daniel Elias; Ortiz, Ada; Mendes Domingos Pereira, Tiago; Popovas, Andrius; Quintero Noda, Carlos; Sainz Dalda, Alberto; Scharmer, Göran B.; Schmit, Donald; Scullion, Eamon; Skogsrud, Håkon; Szydlarski, Mikolaj Marcin; Timmons, R.; Vissers, Gregal Joan Maria; Woods, M. M.; Zacharias, Pia (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2020)
    NASA’s Interface Region Imaging Spectrograph (IRIS) provides high-resolution observations of the solar atmosphere through ultraviolet spectroscopy and imaging. Since the launch of IRIS in June 2013, we have conducted ...
  • Intensity and velocity oscillations in a flaring active region 
    Millar, David C.L.; Fletcher, Lyndsay; Joshi, Jayant (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
    ABSTRACT Chromospheric oscillations can give us insight into the physical environment in the solar atmosphere, both in quiet Sun and flaring conditions. Many authors have reported increases in the prevalence of ...
  • Line formation of He I D3 and He I 10 830 Å in a small-scale reconnection event 
    Libbrecht, Tine; Bjørgen, Johan Pires; Leenaarts, Jorrit; de la Cruz Rodríguez, Jaime; Hansteen, Viggo Haraldson; Joshi, Jayant (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2021)
    Context. Ellerman bombs (EBs) and UV bursts are small-scale reconnection events that occur in the region of the upper photosphere to the chromosphere. It has recently been discovered that these events can have emission ...
  • Magnetic field variations associated with umbral flashes and penumbral waves 
    Joshi, Jayant; de la Cruz Rodriguez, Jaime (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2018)
    Context: Umbral flashes (UF) and running penumbral waves (RPWs) in sunspot chromospheres leave a dramatic imprint in the intensity profile of the Ca II 8542 Å line. Recent studies have focussed on also explaining the ...
  • Observations of magnetic reconnection in the deep solar atmosphere in the Hε line 
    Rouppe van der Voort, Luc; Joshi, Jayant; Krikova, Kilian (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2024)
    Context. Magnetic reconnection in the deep solar atmosphere can give rise to enhanced emission in the Balmer hydrogen lines, a phenomenon known as Ellerman bombs (EBs). It is most common to observe EBs in the H α and H β ...
  • Properties of shock waves in the quiet-Sun chromosphere 
    Mathur, Harsh; Joshi, Jayant; Nagaraju, K.; Rouppe van der Voort, Luc; Bose, Souvik (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2022)
    Context. Short-lived (100 s or less), sub-arcsec to a couple of arcsec sized features of enhanced brightenings in the narrowband images at the H 2V and K 2V positions of the Ca  II H&K lines in the quiet Sun are known ...
  • Properties of ubiquitous magnetic reconnection events in the lower solar atmosphere 
    Joshi, Jayant; Rouppe van der Voort, Luc (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2022)
    Context. Magnetic reconnection in the deep solar atmosphere can give rise to enhanced emission in the Balmer hydrogen lines, a phenomenon referred to as Ellerman bombs. Recent high-quality Hβ observations indicate that ...
  • Signatures of ubiquitous magnetic reconnection in the deep atmosphere of sunspot penumbrae 
    Rouppe van der Voort, Luc; Joshi, Jayant; de Jorge Henriques, Vasco Manuel; Bose, Souvik (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2021)
    Context. Ellerman bombs are regions with enhanced Balmer line wing emission and mark magnetic reconnection in the deep solar atmosphere in active regions and the quiet Sun. They are often found in regions where opposite ...
  • Signatures of ubiquitous magnetic reconnection in the lower solar atmosphere 
    Joshi, Jayant; Rouppe van der Voort, Luc; de la Cruz Rodriguez, Jaime (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2020)
    Ellerman Bomb-like brightenings of the hydrogen Balmer line wings in the quiet Sun, also known as quiet Sun Ellerman bombs (QSEBs), are a signature of the fundamental process of magnetic reconnection at the smallest ...
  • Spicules and downflows in the solar chromosphere 
    Bose, Souvik; Joshi, Jayant; de Jorge Henriques, Vasco Manuel; Rouppe van der Voort, Luc (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2021)
    Context. High-speed downflows have been observed in the solar transition region (TR) and lower corona for many decades. Despite their abundance, it has been hard to find signatures of such downflows in the solar chromosphere. ...