Space physics

Space physics and solar-terrestrial relationships

Our activities are directed toward conducting research and training young scientists in space physics, with a focus on the physics of the magnetosphere, the Sun and the interplanetary medium, as well as emerging issues in Space Weather.

Montage of 25 images captured by SOHO. (SOHO/ESA/NASA)

Solar variability and its effects on circumterrestrial space

The Sun has a cycle of activity related to the variation of magnetic fields on its surface; several phenomena are linked, including irradiance variation, solar flares and coronal mass ejections.

Variation in solar irradiance and effects on Earth's atmosphere

The Sun exhibits a variation in the radiation emitted during the activity cycle, related to the presence of active regions on its surface. This variation is very small when observed over the entire electromagnetic spectrum but is most significant in the ultraviolet region and influences ozone production processes in the Earth's stratosphere.
We studied these relationships by analyzing time series of solar irradiance observations made aboard artificial satellites (SOLSTICE experiment) using some spectral techniques to highlight correlations between irradiance variations in the UV spectrum and defining an equivalent of the color index used in astronomy, defined for the FUV (Far UltaViolet) and MUV (Medium UltraViolet) bands, and another widely used index that is the variation of the intensity ratio in the minima and wings of the MgII spectral line, comparing them with stratospheric ozone densities.

Solar flares forecasting

This activity focuses on the development of small telescopes capable of simultaneously observing the entire disk of the Sun at different wavelengths, allowing for evaluation of the velocity and magnetic fields along the line of sight at different heights in the solar atmosphere and possible relations with the instabilities and dynamics associated with the formation of solar flares, thus serving as a precursor to such explosive and intense phenomena.

Il collega Stuart M. Jefferies e il telescopio MOTH II in Antartide (fonte Georgia State University)

Il collega Stuart M. Jefferies e il telescopio MOTH II in Antartide (fonte Georgia State University)

In collaboration with colleagues from Georgia State University, the Jet Propulsion Laboratory (JPL), the European Space Agency and the University of Tor Vergata, we developed the pipeline to analyze full-disk solar images observed with the MOTH II telescope, which operated at the Amundsen Antarctic Station for two different observing campaigns (2016-2017 and 2017-2018). This telescope works using magneto-optical filters (MOFs) in two different wavelength bands.

Il TSST nella fase di test presso il Laboratorio di Fisica solare dell'Università di Tor Vergata

The Tor Vergata Synoptic Solar Telescope (TSST) is a compact, robotic multichannel instrument designed to conform to the main objectives described in the SPRING project, developed under the European Union-funded H2020-SOLARNET program and focuses on a preliminary design study of a synoptic solar observing facility. The TSST currently consists of two full-disk Sun observing instruments, an H-alpha telescope and a telescope based on a magneto-optical potassium filter (MOF) (KI D1) operating at 769.9 nm. The TSST is designed to be later upgraded with a second MOF channel.

Interaction of coronal mass ejections with the Earth and the circumterrestrial environment

Coronal mass ejections (CMEs) are the most energetic events occurring on the Sun and release huge amounts of plasma into interplanetary space at very high velocities. A CME that encounters the Earth on its path can interact with the Earth's magnetosphere, becoming an important source of risk, especially for space and terrestrial technological infrastructures. For this reason, the need to properly understand the mechanisms of formation, launch and propagation of CMEs from the Sun has become a key task in current space weather science. Our group, together with the Solar Physics group at Tor Vergata University, is collaborating on implementing numerical models of increasing complexity, from simplified dynamical models to more elaborate fluid dynamics simulations, to provide such predictive information.

Plasmasphere monitoring

The plasmasphere is a torus-like region of cold plasma (energy of the order of 1 eV) that encircles the Earth and extends from 1000 km up to 4-6 Earth radii (R⊕). Although the cold plasma is not a direct threat to human activity in space, its interaction with more energetic particle populations, such as ring currents and radiation belts, can determine space weather conditions. It is, therefore, essential to continuously monitor the state of the plasmasphere for nowcasting and forecasting purposes.

A technique to remotely sense the equatorial plasma mass density in the near-Earth space is based on spectral analysis of Ultra Low Frequency (ULF) magnetic signals recorded by magnetometer arrays on the ground. The technique uses data collected by pairs of magnetometers slightly separated in latitude and approximately aligned along the same magnetic meridian. A latitudinally extended network can monitor the radial dependence of the equatorial plasma mass density along with the longitudinal sector identified by the array. The procedure can be operative on a near real-time basis. EMMA, the European quasi-Meridional Magnetometer Array, is a prototype of this monitoring system established in 2012 in the PLASMON FP7 European project framework. It currently consists of 27 stations and is suitable for determining plasma mass densities for an extended range of L values (1.6-6.2R⊕). 1-sec data are collected and automatically processed every 15 min with an automated procedure to infer the equatorial plasma mass densities.

Solar wind-magnetosphere interaction

The solar wind variability reflects the variability of the solar atmosphere and manifests itself through the solar cycle by different geoeffective structures.
During the declining phase of the solar cycle and near the minimum, high speed streams originate from stable coronal holes. Due to the Sun rotation, they interact periodically (~27 days) with the Earth’smagnetosphere producing a recurrent geomagnetic activity. Near the solar maximum, geomagnetic perturbations are mostly driven by transient structures related to coronal mass ejections.
The interaction of the solar wind structures with the Earth’s magnetosphere produces both global and local geomagnetic field perturbations which occur at different time scales.

ULF waves

Ultra Low Frequency (ULF) fluctuations of the geomagnetic field lines characterize the geomagnetic activity in the frequency range ~1 mHz - 5 Hz. They are observed both in the magnetosphere and on the ground. ULF waves at lower frequencies (1.7-6.7 mHz, Pc5 pulsations on the ground) are believed to be driven by the Kelvin Helmholtz instability along the flanks of the magnetopause and/or by solar wind pressure variations associated to high speed streams. These waves are involved in the acceleration of magnetospheric electrons in the radiation belts.
The main source for ULF waves in the mid-frequency range (10–100 mHz, Pc3 pulsations) is supposed to be represented by upstream waves. They are generated in the Earth's foreshock region by a wave-particle interaction between already existing waves and solar wind protons reflected off the bow shock along the interplanetary magnetic field lines.
ULF higher frequency waves (0.1-5 Hz, magnetospheric EMIC waves, Pc1-2 pulsations on the ground) are generated near the plasmapause by unstable distributions of ring current ions and near the magnetopause by solar wind pressure pulse driven instability. Electromagnetic ion-cyclotron (EMIC) waves are responsible for relativistic electron precipitations at high latitude.

Development of sensors for the characterization of space plasmas

The group collaborates closely with the National Institute of Astrophysics (INAF-IAPS) and the INFN of Rome Tor Vergata to develop sensors for the characterization of space plasmas both from the point of view of the electromagnetic field and plasma parameters (density, velocity, composition, temperature, etc.).

In this field, the group is involved in the CSES-Limadou satellite mission and the CUBE mission (ESA), for which it is building an electric field detector, a plasma analyzer and a Langmuir Probe.

The sensors are developed and calibrated inside the INAF-IAPS plasma chamber: a facility capable of reproducing a large volume of ionospheric and interplanetary plasma (solar wind). Its peculiarity is mainly due to sources that produce plasma with values of characteristic parameters (i.e., density, electron temperature, and ionic energies) in the range of those found in the ionosphere and interplanetary space.

Effects on the polar atmosphere

Geomagnetic perturbations significantly influence the atmosphere, particularly at high latitudes, where changes in the electrical potential of the polar cap occur, and energetic electrons precipitate along local geomagnetic field lines.

The precipitation of energetic particles can change by ionization the electrical conductivity in the lower atmosphere. The resulting modulation of the current density flowing from the upper boundary (up to 60 km) through the troposphere to the ground in the Global Electric Circuit (GEC) could affect the cloud cover, thus influencing atmospheric dynamics. This approach does not require energy transfer through the upper atmosphere and is characterized by a rapid response (< 1 day).

The MAgnetosphere Ionosphere and Geomagnetic Induced Currents (MA.I.GIC.) model.

During a geomagnetic storm, rapid and very intense changes in the Earth's magnetic field generate intense ground-induced currents (GICs) that can cause damage and, in the most extreme cases, destroy both modern technological infrastructure (such as national power grids, gas pipelines, etc.) and telecommunications systems.

The MA.I.GIC. model enables the assessment of GICs and the discrimination between currents of magnetospheric and ionospheric origin, which provides a better understanding of how various current systems impact various infrastructures during periods of high solar activity, increasing the ability to assess the associated risk.

Magnetosphere-Ionosphere-Lithosphere (M.I.L.C.) coupling model.

Earthquakes pose the greatest threat to modern society in terms of possible loss of life and destruction of urbanism. Over the past decade, the number of possible observations of anomalous signals in the atmosphere and magnetosphere hypothetically attributable to earthquakes has grown. However, the lack of a mathematical model has always prevented such signals from being causally coupled to seismic events.

M.I.L.C. is the first analytical model capable of co-seismically interpreting and predicting possible signals in the atmosphere, ionosphere and magnetosphere. It is based on the generation of a gravity-acoustic wave in the atmosphere that mechanically interacts with the ionosphere generating an 'instability of the local plasma distribution across a pressure gradient. Such plasma variation brings the ionosphere into a "meta-stable" state by developing both a plasma wave and an electromagnetic wave that, in turn, interact with the Earth's magnetosphere by changing the resonance frequency of the magnetospheric field line hinged at the epicenter of the earthquake.