Ionospheric Boundary Research Articles

A novel piecewise linear transformation to moderate regional boundary effect on Real-Time regional ionospheric map (RT-RIM)

RT-RIM with high accuracy and dense spatiotemporal resolution of the ionospheric total electron content is crucial to diverse real-time GNSS applications. However, the uneven ionospheric pierce points distribution and boundary effect severely restrict the RT-RIM accuracy. We dedicate to the rapid and straightforward method to address the limited accuracy issue caused by the two crucial challenges. A novel piecewise linear transformation-adjusted spherical cap harmonic (PLT-ASCH) method is proposed to moderate the localized accuracy decrease in various latitudes areas for both active and stable ionospheric conditions. Especially, in the active ionospheric condition, the RMS improvements referring to IGS products are about 38.85%, 17.04%, 16.73% in Europe and 53.12%, 4.36%, 4.35% in South America, comparing to the inverse distance weighting, ASCH, and adjusted spherical harmonics adding Kriging methods. Moreover, the RMS improvements referring to differential slant TEC are about 48.11%, 16.53%, 16.99% in Europe and 61.01%, 4.87%, 4.33% in South America.

The Martian Ionospheric Response to the Co‐Rotating Interaction Region That Caused the Disappearing Solar Wind Event at Mars

AbstractAn unusually low density solar wind event was observed in December 2022 moving past both Earth and Mars. The source was traced back to a coronal hole and active region on the Sun's surface. The resulting solar wind lead to the development of a co‐rotating interaction region (CIR) and trailing rarefaction region that lasted for multiple solar rotations. Within this structure, the solar wind conditions, including density, velocity, and magnetic field magnitude and orientation drastically changed. In this study we analyze the response of the Martian ionosphere using MAVEN data to these changing solar wind conditions. The low density solar wind region associated with the December event resulted in the expansion of the Martian ionospheric boundaries. We show that the ion composition boundary (ICB) is located at extreme altitudes that are beyond previously observed locations from the MAVEN mission between 2015 and 2018. Furthermore, the boundary between shocked solar wind and the Martian ionosphere identified using electron and ion data moved together on the dayside of the planet with the changing solar wind conditions. However, at the flank region these boundaries do not move together, and we show here that the decoupling of the two boundaries may be the result of a change in the interplanetary magnetic field azimuthal angle.

Examining the Applicability of Direct Analytic Method (DAM) to Normal Modes of Poloidal Oscillations Under Symmetric and Asymmetric Boundary Conditions

AbstractA working Direct Analytic Method (DAM) model is envisaged to explain the normal modes of poloidal Alfven waves in the Earth's magnetosphere. The model solves the ideal, cold, magnetohydrodynamic (MHD) equations associated with transverse components of the magnetic perturbations in a dipolar magnetic field. DAM model is used to study the transverse poloidal waves in different regions of magnetosphere characterized by their L‐value and different plasma variability. The plasma density distribution is assumed to be governed by the standard power law, 1/rm, where r is the geocentric distance of any point of interest on the field line and m is the density index. The eigen frequencies and spatial structures are obtained analytically under different ideal ionospheric boundary conditions and the results are compared with the numerical solutions to establish the validity of the model. DAM, being an analytic model, is used to explain the distinctive structural features of transverse poloidal waves which are obtained under different boundary conditions, for different density indices. Furthermore, the application of the analytic model in the computation of eigen frequency as well as plasma density is demonstrated under different observational scenario.

Regarding the Theory of Power Lines Emission Propagation to the Space

AbstractThe analytical theory is presented that describes the propagation of power lines emission (PLE) with frequency of 50/60 Hz in the heights range from the Earth surface to the magnetosphere. Validation of the theory is made by the comparison with earlier published results of numerical modeling. It is shown that the actual source of emission is a magnetic dipole formed by the power line current and by the secondary image current in the ground. The emission is propagating to the lower boundary of ionosphere, where its main part is reflected back, but some of the energy (a few percent) penetrates into the ionosphere. There it is transformed into a quasi‐flat whistler wave. The generation of current in ground and the reflection from the ionosphere are the main factors that reduce the emission into space. In the ionosphere wave fronts propagate approximately vertically, and the energy propagates in a certain direction that depends on the geomagnetic field inclination. Thus, the ionosphere acts as a focusing system that collects PLE into a unidirectional beam. The PLE intensity does not change with altitude within the total range of ionospheric heights. In the magnetosphere PLE is transformed to both magnetosonic and Alfvén waves and the emission splits into two rays: one propagates along the wave vector and the other one—along the geomagnetic field lines. A set of analytical solutions is presented allowing determining the change in PLE parameters with altitude depending on the source parameters and ionospheric conditions.

Effects of the Ionospheric Conductance on the Dynamics of the Magnetotail

AbstractWe have carried out a series of numerical experiments designed to evaluate the sensitivity of global magnetohydrodynamic simulations to changes in ionospheric conductance. We multiplied the precipitating energy fluxes due to both strong pitch angle scattering and parallel currents by constant factors in the Robinson et al. (1987, https://doi.org/10.1029/JA092iA03p02565) model and used them as input to a simulated substorm interval on 14 March 2008. We also used the Kaeppler et al. (2015, https://doi.org/10.1002/2015JA021396) model. When we reduced the energy fluxes by a factor of about three (0.34), the agreement on substorm location was best. Larger conductances led to onset at later local times. For multiplication factors greater than one, the magnetotail became line tied and no flows entered the inner magnetotail region. Relatively small (<50%) differences in the conductances lead to major changes in the tail configuration. We calculated auroral indices from the simulations and compared them to observations. None of the models reproduced the DP1 system but, we obtained much better agreement with the observed DP2 system. The model with the basic Robinson formula gave the best agreement with the DP2 system. We also ran a generic simulation with constant solar wind and southward IMF using the basic Robinson et al. model. The results were very similar to those of the event simulation suggesting that the changes were due to the ionospheric boundary condition. In the simulation, the energy flux obtained by assuming strong pitch angle scattering makes a larger contribution to the conductance than the field‐aligned current energy flux.

Ionospheric Boundaries Derived From Auroral Images

AbstractThis paper presents updated methods for locating the Poleward and Equatorward Auroral Luminosity Boundaries (PALB and EALB) directly from IMAGE Far UltraViolet (FUV) images of the Northern Hemisphere auroral oval. Separate boundaries are determined from images measured at different FUV wavelengths. In addition, new methods for indirectly estimating the Open‐Closed magnetic field line Boundary (OCB) and the Equatorward Precipitation Boundary (EPB) locations are presented; these new boundaries are derived from a combination of the auroral luminosity boundary estimates with statistical latitudinal offsets derived from comparisons with low‐altitude spacecraft Particle Precipitation Boundaries (PPBs). Subsequently, we derive new circle model fits for all these boundary data sets, as well as new quality control criteria for these model fits. The suitability of circle fits for each of the data sets is discussed, and the OCB and PALB circle fits are validated against the Convection Reversal Boundary (CRB), as measured by low‐altitude in situ spacecraft. All the new boundary data sets, covering the epoch May 2000 to October 2002, are freely available online.

Role of ionospheric Pedersen conductance and its gradient in field-aligned currents

Field-aligned current (FAC) is one of the most important aspects in the coupling of magnetosphere and the ionosphere. This paper presents a systematic numerical study of the magnetospheric and ionospheric influences on the evolution and modification of FACs, with focus on the role of ionospheric Pedersen conductance and its gradient. FACs are typically generated in the magnetosphere and are carried into the ionosphere by Alfvén waves. During their reflection from the ionosphere, these FACs are modified. The nature of modifications depends on the magnitude and distribution of ionospheric Pedersen conductance. A uniform ionosphere, having a high Pedersen conductance, enhances such a magnetospheric FAC strongly. For conductance-gradients perpendicular to the wave-polarization, FACs are generated after the reflection of simple Alfvénic perturbations, which are not carrying any FACs. A suitable arrangement of ionospheric Pedersen conductance can create a pair of antiparallel FACs, with consequent generation of a strong Pedersen current at the ionospheric boundary. For conductance-gradients along the polarization of the wave, the steady state velocity perturbation assumes an average value of the imposed Pedersen conductance over the entire region after reflection from the ionosphere. This configuration is comparable to the situation where the Cowling conductance operates.

Links of the Plasmapause With Other Boundary Layers of the Magnetosphere: Ionospheric Convection, Radiation Belt Boundaries, Auroral Oval

The plasmapause marks the limit of the plasmasphere and is characterized by a sudden change in plasma density. This can influence the other regions of the magnetosphere, including due to different waves circulating inside and outside the plasmasphere. In the present work, we first compare the positions of the plasmapause measured by the NASA Van Allen Probes in 2015 with those of the Space Weather Integrated Forecasting Framework plasmasphere model (SPM). Using the Van Allen Probes and other satellite observations like PROBA-V, we investigate the links that can exist with the radiation belt boundaries. The inward motion of the outer radiation belt associated with sudden flux enhancements of energetic electrons can indeed be directly related to the plasmapause erosion during geomagnetic storms, suggesting possible links. Moreover, the position of the plasmapause projected in the ionosphere is compared with the ionospheric convection boundary. The equatorward motion of the plasmapause projected in the ionosphere is related to the equatorward edge motion of the auroral oval that goes to lower latitudes during storms due to the geomagnetic perturbation, like the low altitude plasmapause and the outer radiation belt. The links between these different regions are investigated during quiet periods, for which the plasmasphere is widely extended, as well as during geomagnetic storms for which plumes are generated, and then afterwards rotates with the plasmasphere. The magnetic local time dependence of these boundaries is especially studied on March 14, 2014 after a sudden northward turning of the interplanetary magnetic field (IMF) and for the geomagnetic storm of August 26, 2018, showing the importance of the magnetic field topology and of the convection electric field in the interactions between these different regions eventually leading to the coupling between magnetosphere and ionosphere.

Role of Ionospheric Pedersen Conductance and its Gradient in Field-Aligned Currents

Field-aligned current (FAC) is one of the most important aspects in the coupling of magnetosphere and the ionosphere. This paper presents a systematic numerical study of the magnetospheric and ionospheric influences on the evolution and modification of FACs, with focus on the role of ionospheric Pedersen conductance and its gradient. FACs are typically generated in the magnetosphere and are carried into the ionosphere by Alfven waves. During their reflection from the ionosphere, these FACs are modified. The nature of modifications depends on the magnitude and distribution of ionospheric Pedersen conductance. A uniform ionosphere, having a high Pedersen conductance, enhances such a magnetospheric FAC strongly. For conductance-gradients perpendicular to the wave-polarization, FACs are generated after the reflection of simple Alfvenic perturbations, which are not carrying any FACs. A suitable arrangement of ionospheric Pedersen conductance can create a pair of antiparallel FACs, with consequent generation of a strong Pedersen current at the ionospheric boundary. For conductance-gradients along the polarization of the wave, the steady state velocity perturbation assumes an average value of the imposed Pedersen conductance over the entire region after reflection from the ionosphere. This configuration is comparable to the situation where the Cowling conductance operates.

Magnetotail‐Inner Magnetosphere Transport Associated With Fast Flows Based on Combined Global‐Hybrid and CIMI Simulation

AbstractUsing the combined Auburn global hybrid simulation code in 3‐D (ANGIE3D) and the Comprehensive Inner Magnetosphere‐Ionosphere (CIMI) model, we investigate the self‐consistent connection of fast flow injections from the tail plasma sheet and the inner magnetosphere under a southward IMF. In the dynamic run, the hybrid results provide the CIMI model with 3‐D magnetic field and the electric potential at the high latitude ionosphere boundary as well as the full ion phase space distribution function at the CIMI outer boundary at the equator. The simulation shows that magnetotail reconnection, which has a dawn‐dusk size of ∼1–5 RE, recurs with a period of several minutes, resulting in recurring localized fast flow injections. Strong ion temperature anisotropy and non‐Maxwellian distributions are present in the fast flows, and the braking of fast flows due to the dipole‐like field results in further perpendicular heating in the injection sources. Multiple fast flow injections lead to multiple peaks in the particle fluxes in the inner magnetosphere as well as layers of upward and downward field‐aligned currents at the ionosphere, and low energy particles penetrate deeper radially than the high energy particles. The combined ANGIE3D‐CIMI model can be used to calculate the global kinetic physics that contains both Region‐1 and Region‐2 field‐aligned currents.

Expansion and Shrinking of the Martian Topside Ionosphere

AbstractThe observations made by the Mars Atmosphere and Volatile EvolutioN spacecraft in the topside (≥200 km) ionosphere of Mars show that this region is very responsive to the variations of the external (solar extreme ultraviolet flux, solar wind, and interplanetary magnetic field [IMF]) and internal (the crustal magnetic field) drivers. With the growth of the solar irradiance the ionosphere broadens while with increase of the solar wind dynamic pressure it shrinks. As a result, the upper ionospheric boundary at solar zenith angles of 60–70° can move from ∼400 to ∼1,200 km. Similar trends are observed at the nightside ionosphere. At Pdyn ≥ 1–2 nPa the nightside ionosphere becomes very fragmented and depleted. On the other hand, the ion density in the nightside ionosphere significantly (up to a factor of 10) increases with the rise of the solar extreme ultraviolet flux. Large‐amplitude motions of the topside ionosphere also occur with variations of the value of the cross‐flow component of the IMF. The upper dayside ionosphere at altitudes of more than 300–400 km is sensitive also to the direction of the cross‐flow component of the IMF or, correspondingly, to the direction of the motional electric field in the solar wind. The ionosphere becomes very asymmetrical with respect to the Vsw×BIMF direction and the asymmetry strongly enhances at the nightside. The topside ionosphere above the areas with strong crustal magnetic field in the dayside southern hemisphere is significantly denser and expands to higher altitudes as compared to the ionosphere above the northern nonmagnetized lowlands. The crustal magnetic field also protects the nightside ionosphere from being filled by plasma transported from the dayside. The draping IMF penetrates deeply into the ionosphere and actively influences its structure. Weak fields and, correspondingly, weak magnetic field forces only slightly affect the ionosphere. With increase of the induced magnetic field strength the transport motions driven by the magnetic field pressure and field tensions seem to be intensified and we observe that the local ion densities at the dayside considerably decrease. A different trend is observed at the nightside. The ion density in the nightside ionosphere above the northern lowlands is higher than in the southern hemisphere indicating that plasma transport from the dayside is the main source of the nightside ionosphere. Nonstop variations in the solar wind, the IMF and the solar irradiance together with planetary rotation of the crustal magnetic field sources lead to a continuous expansion/shrinking and reconfiguration of the topside ionosphere of Mars.

The Formation of Electron Heat Flux Over the Sunlit Quiet Polar Cap Ionosphere

AbstractWe consider a new mechanism for the thermal electron heat fluxes formation over the sunlit polar cap in the presence of the potential jumps that are created by the photoelectron escape along the open magnetic field lines. Photoelectrons traveling into the magnetosphere experience small Coulomb collisional scattering, and the low‐energy part of their spectra becomes trapped between the potential jump and upper ionosphere creating the thermal electron energy fluxes that support the formation of electron temperature at the ionospheric altitudes. This mechanism eliminates the need for the customary practice of assuming arbitrary electron heat fluxes at the upper ionospheric boundary in order to explain the measured electron temperature in the topside ionosphere.

Scientific Goals and In-orbit Performance of the High-energy Particle Detector on Board the CSES

Abstract The China Seismo-Electromagnetic Satellite (CSES) aims to monitor electromagnetic, particle, and plasma perturbations in the iono-magnetosphere and inner Van Allen radiation belts originated by electromagnetic sources external and internal to the geomagnetic cavity, cosmic rays, and solar events. In particular, the objective of the space mission is to investigate lithosphere–atmosphere–ionosphere coupling mechanisms (including the effects of lightning, earthquakes, volcanoes, and artificial electromagnetic emissions) that induce perturbations of the top side of the ionosphere and lower boundary of the radiation belts. To this purpose, the mission has been conceived to take advantage of a multi-instrument payload comprising nine detectors for the measurement of electromagnetic field components, plasma parameters, and energetic particles, as well as X-ray flux. The Italian team participating in the CSES mission has built one of these devices, the High-Energy Particle Detector (HEPD), for high-precision observations of electrons, protons, and light nuclei. During its trip along the orbit, and thanks to the large set of detectors operated on board, CSES completely monitors the Earth, acting as an excellent instrument for space weather. The satellite was launched on 2018 February 2, with an expected life span of 5 yr. This article describes the CSES mission with a particular focus on the HEPD apparatus and its in-flight performance.

Effects of the solar wind and the solar EUV flux on O+ escape rates from Venus

We investigate dependences of O+ escape rates from Venus both on the solar wind and the solar extreme ultraviolet (EUV) flux by using the 8.5-year dataset (May 2006 to December 2014) of the Ion Mass Analyzer and the magnetometer aboard Venus Express. We examine the O+ escape rates for 8 different conditions depending on the solar wind's dynamic pressure, the magnitude of the motional electric field, and the solar F10.7 index which is a good indicator for the solar EUV flux. We find that the O+ escape rates are mainly controlled by the motional electric field and the solar EUV flux in the magnetosheath. We suggest that the ion pickup by the motional electric field is the main ion escape process in the magnetosheath. On the other hand, in the induced magnetosphere, the O+ escape rates are controlled by not only the solar wind and the solar EUV flux but also return flows. We find that the return flows become dominant in the magnetotail in the solar maximum period, which results in reducing the net escape rates in the induced magnetosphere. As a result, net escape rates tend to become larger in the solar minimum period than those in the solar maximum period. Further analysis of the magnetic field shows that the return flows are preferably observed when the magnetic field component along the Venus-Sun line reverses multiple times in the magnetotail. We suggest that ionospheric irregular structures or IMF sector boundary crossings form the fine scale anti-parallel draping pattern of the interplanetary magnetic field (IMF), and this causes ion acceleration towards Venus due to the magnetic tension force or magnetic reconnections. Another possibility is precipitations of O+ pickup ions on the nightside of Venus under the fine structure of IMF. Since the return flows significantly affect the O+ escape rates from Venus, it is important to study not only long-term transition of ion outflow from Venus but also return flows to estimate the net ion loss from Venus over the long history of the solar system.

On the Existence of Ionospheric Feedback Instability in the Earth's Magnetosphere‐Ionosphere System

AbstractThe ionospheric feedback instability (IFI) has been considered one of the main generation mechanisms for large‐amplitude ultralow frequency waves and small‐scale field‐aligned currents in the auroral and subauroral regions for more than 40 years. Sydorenko and Rankin (2017, https://doi.org/10.1002/2017GL073415) have recently challenged the very existence of the IFI for any realistic geophysical conditions in the Earth's ionosphere‐magnetosphere system. Because this conclusion contradicts numerous theoretical, numerical, and experimental works successfully used IFI to explain and predict results from observations for more than four decades, it deserves special attention. We show that this conclusion is mainly based on the specific ionospheric density profile and boundary conditions used in two runs of simulations presented in Sydorenko and Rankin (2017), and the generalization of this result is not justified. The effect of the collisions between ionospheric ions and neutrals on the development of the instability has been well studied since 1981, and these studies demonstrate that it does not prevent the development of the instability. Furthermore, excellent agreement of the theoretical and numerical results with observations verify without doubt the IFI existence and significance in the Earth's magnetosphere‐ionosphere system.

A Statistical Study of Ionospheric Boundary Wave Formation at Venus

AbstractPrevious missions to Venus have revealed that encounters with plasma irregularities of atmospheric origin outside the atmosphere are not uncommon. A number of mechanisms have been proposed to discuss their origins as well as their roles in the atmospheric evolution of Venus. One such mechanism involves an ionopause with a wavelike appearance. By utilizing the magnetic field and plasma data from Venus Express, we present the first observational statistical analysis of the ionospheric boundary wave phenomena at Venus using data from 2006 to 2014. Results from the minimum variance analysis of all the photoelectron dropout events in the ionosphere reveal that the ionopause of Venus does not always appear to be smooth but often exhibits a wavelike appearance. In the northern polar region of Venus, the normal directions of the rippled ionospheric boundary crossings lie mainly in the terminator plane with the largest component predominantly along the dawn‐dusk (YVSO) direction. The average estimated wavelength of the boundary wave is 212 ± 12 km, and the average estimated velocity difference across the ionopause is 104 ± 6 km/s. The results suggest that the rippled boundary is a result of Kelvin‐Helmholtz instability. Analysis reveals a correlation between the normal directions and the locations of the boundary wave with respect to Venus. This indicates that the draping of magnetic field lines may play a role in enhancing the plasma flow along the dawn‐dusk direction, which could subsequently set up a velocity shear that favors the excitation of ionospheric boundary wave by the Kelvin‐Helmholtz instability along the dawn‐dusk direction.

MAVEN Observations of the Response of Martian Ionosphere to the Interplanetary Coronal Mass Ejections of March 2015

AbstractThe Mars Atmosphere and Volatile EvolutioN spacecraft provides an opportunity to observe the response of the Martian upper atmosphere to the passage of interplanetary coronal mass ejections. We study the response of Martian ionosphere to two successive solar disturbances during 3 and 4 March and 8 and 9 March 2015 using the observations from Neutral Gas and Ion Mass Spectrometer and Langmuir Probe and Waves aboard Mars Atmosphere and Volatile EvolutioN. During these events, the ionospheric boundary was significantly lowered. During 3 March the ionopause is seen to be at a lower altitude, compared to that during 8 March. The higher ionopause seen on 8 March could be due to the sustained effect of heating and inflation by the 3 March interplanetary coronal mass ejection event or due to the heating by the enhanced particle precipitation. The comparison of the O+/O ratio indicates that there is a preferential decrease of O and a relative enhancement in O+, probably due to increased dissociative recombination and charge exchange as a result of the higher solar wind densities during the 3 March event.

Triangulation and Coupling of Gigantic Jets Near the Lower Ionosphere Altitudes

AbstractCoordinated TLE (transient luminous event) optical observations in Taiwan have been held since 2011, with an aim to achieve triangulation. Currently, there are four observation stations with baselines varying from 100 to 400 km between them. The system recorded eight gigantic jets (GJs) that were recorded by at least two stations on the night of 20 August 2014. The weather radar data indicate that these GJs occurred around the troposphere overshooting tops of a vigorous cumulonimbus cloud. A leader‐to‐streamer transition was discerned as the appearance of these GJs changed from jet‐like (leader) to fan‐like (streamer) at ~40 km altitude. Most of these GJs terminated at the lower ionosphere boundary (80–90 km), but one GJ topped with a 10 km thick diffuse region extended higher than 100 km. Moreover, three sets of the GJs occurred within 0.5–100 s in the same general region. The residual plasma patches from the preceding GJs appear to cause the subsequent GJs to contain more bead structures and to be brighter. Also, three streamer columns of a subsequent GJ that occurred more than 100 s after the preceding GJ were identified to have rebrightened at 55 to 70 km altitudes. The rebrightened streamers and the bead structure increments in the subsequent GJs suggest that there were GJ‐produced long‐lasting plasma patches in the mesosphere.

Observation and Numerical Simulation of Cavity Mode Oscillations Excited by an Interplanetary Shock

AbstractCavity mode oscillations (CMOs) are basic magnetohydrodynamic eigenmodes in the magnetosphere predicted by theory and are expected to occur following the arrival of an interplanetary shock. However, observational studies of shock‐induced CMOs have been sparse. We present a case study of a dayside ultralow‐frequency wave event that exhibited CMO properties. The event occurred immediately following the arrival of an interplanetary shock at 0829 UT on 15 August 2015. The shock was observed in the solar wind by the Time History of Events and Macroscale Interactions during Substorms‐B and ‐C spacecraft, and magnetospheric ultralow‐frequency waves were observed by multiple spacecraft including the Van Allen Probe‐A and Van Allen Probe‐B spacecraft, which were located in the dayside plasmasphere at L ∼1.4 and L ∼ 2.4, respectively. Both Van Allen Probes spacecraft detected compressional poloidal mode oscillations at ∼13 mHz (fundamental) and ∼26 mHz (second harmonic). At both frequencies, the azimuthal component of the electric field (Eϕ) lagged behind the compressional component of the magnetic field (Bμ) by ∼90°. The frequencies and the Eϕ‐Bμ relative phase are in good agreement with the CMOs generated in a dipole magnetohydrodynamic simulation that incorporates a realistic plasma mass density distribution and ionospheric boundary condition. The oscillations were also detected on the ground by the European quasi‐Meridional Magnetometer Array, which was located near the magnetic field footprints of the Van Allen Probes spacecraft.

Perturbations to the lower ionosphere by tropical cyclone Evan in the South Pacific Region

AbstractVery low frequency (VLF) electromagnetic signals from navigational transmitters propagate worldwide in the Earth‐ionosphere waveguide formed by the Earth and the electrically conducting lower ionosphere. Changes in the signal properties are signatures of variations in the conductivity of the reflecting boundary of the lower ionosphere which is located in the mesosphere and lower thermosphere, and their analysis is, therefore, a way to study processes in these remote regions. Here we present a study on amplitude perturbations of local origin on the VLF transmitter signals (NPM, NLK, NAA, and JJI) observed during tropical cyclone (TC) Evan, 9–16 December 2012 when TC was in the proximity of the transmitter‐receiver links. We observed a maximum amplitude perturbation of 5.7 dB on JJI transmitter during 16 December event. From Long Wave Propagation Capability model applied to three selected events we estimate a maximum decrease in the nighttime D region reference height (H′) by ~5.2 km (13 December, NPM) and maximum increase in the daytime D region H′ by 6.1 km and 7.5 km (14 and 16 December, JJI). The results suggest that the TC caused the neutral densities of the mesosphere and lower thermosphere to lift and sink (bringing the lower ionosphere with it), an effect that may be mediated by gravity waves generated by the TC. The perturbations were observed before the storm was classified as a TC, at a time when it was a tropical depression, suggesting the broader conclusion that severe convective storms, in general, perturb the mesosphere and the stratosphere through which the perturbations propagate.