Engineering topics

Landi, Enrico

Publications and source records attributed to Landi, Enrico.

4 records

NASA NTRS2018

EUV Diagnostics of Optically Thick Plasmas Using the 304 Å Channel

A fundamental limitation of current EUV diagnostic techniques is the need to neglect the He II emission contribution in the 304Å channel. This limits our ability to use strong observations available to us and increases uncertainties in the measurements made. A new EUV diagnostic technique is introduced that accounts for absorption as well as emission contributions from emitting channels such as 304 Å. This new technique can be equally applied to emitting and non-emitting channels, paving the way for more realistic discussion of the heating and energetics of transient plasmas using a wider range of observations. The diagnostic technique is used to compute the dynamics and energetics of a filament eruption observed in the high-cadence SDO/AIA and the associated ICME is observed by ACE/SWICS. The analysis gives us robust measurements of filament dynamics, energetics and its ionization history in the low solar corona. A comparison of these results with results calculated with techniques where He II emission in 304 Å is not considered allowed us to quantify the contribution from emission and comment on the robustness of our method.

EUV↗

NASA NTRS2017

The Sun Radio Imaging Space Experiment (SunRISE)

Radio emission from coronal mass ejections (CMEs) is a di- rect tracer of particle acceleration in the inner heliosphere and potential magnetic connections from the lower solar corona to the larger heliosphere. Energized electrons excite Langmuir waves, which convert into radio emission at the local plasma frequency, with the most intense acceleration thought to occur within 20 RS, but many aspects of this par- ticle acceleration and transport remain poorly constrained. Ground-based arrays would be quite capable of tracking the radio emission associated with CMEs, but absorption by the Earth’s ionosphere limits the frequency coverage of ground-based arrays (n > 15 MHz), which in turn limits the altitudes over which they can track the radio emission ( < 3RS). The state-of-the-art for tracking such emission from space is defined by single antennas (Wind/WAVES, Stereo/SWAVES), in which the tracking is accomplished by assuming a frequency-to-density mapping; there has been some success in triangulating the emission between the spacecraft, but considerable uncertainties remain. We describe the Sun Radio Imaging Space Experiment (Sun- RISE) mission concept: A constellation of small spacecraft in a geostationary graveyard orbit designed to localize and track radio emissions in the inner heliosphere. Each space- craft would carry a receiving system for observations be- low 25 MHz, and SunRISE would image CMEs more than a few solar radii from the Sun.

Zaslavsky, Arnaud↗

NASA NTRS2006

UV Observations of Prominence Activation and Cool Loop Dynamics

In this paper we investigate the thermal and dynamic properties of dynamic structures in and around a prominence channel observed on the limb on 17 April 2003. Observations were taken with the Solar and Heliospheric Observatory's Solar Ultraviolet Measurements of Emitted Radiation (SOHO/SUMER) in lines formed at temperatures from 80,000 to 1.6 MK. The instrument was pointed to a single location and took a series of 90 s exposures. Two-dimensional context was provided by the Transition Region and Coronal Explorer (TRACE) in the UV and EUV and the Kanzelhohe Solar Observatory in H-alpha. Two dynamic features were studied in depth: an activated prominence and repeated motions in a loop near the prominence. We calculated three-dimensional geometries and trajectories, differential emission measure, and limits on the mass, pressure, average density, and kinetic and thermal energies. These observations provide important tests for models of dynamics in prominences and cool (approx. 10(exp 5) K)loops, which will ultimately lead to a better understanding the mechanism(s) leading to energy and mass flow in these solar features.

Kucera, Therese A.↗

NASA NTRS1999

A Direct Comparison Between EUV Coronal Flux and Helium Resonance Line Photon Flux from SOHO/CDS Data

In the wealth of EUV spectroscopic and imaging data gathered by the SOHO and TRACE missions, a prominent role is played by the helium resonance emission. For example, He I lines are among the most intense features in CDS/NIS spectra, while the EIT 304 waveband (dominated by He II emission) is routinely employed to map the structure of the solar chromosphere and transition region. However, no 'standard' model has emerged so far that is able to interpret observed He spectra/images to a satisfactory degree of self-consistency. Recent research on the problem of the formation of the solar helium spectrum tends to rule out a dominant role of coronal radiation in exciting He resonance lines. However, while evidence for this result is strong, it is based on indirect tests. Here we present a preliminary assessment of this issue based on a more direct approach, which involves a measure with CDS/GIS of the photoionizing EUV radiation. This measure can be directly compared with the observed flux in the main He I and He II resonance lines observed with CDS/NIS2.

Andretta, V.↗