Quiet Time Periods Research Articles

MAGE Model Simulation of the Pre‐Reversal Enhancement and Comparison With ICON and Jicamarca ISR Observations

AbstractUsing the latest coupled geospace model Multiscale Atmosphere‐Geospace Environment (MAGE) and observations from Jicamarca Incoherent scatter radar (ISR) and ICON ion velocity meter (IVM) instrument, we examine the pre‐reversal enhancement (PRE) during geomagnetic quiet time period. The MAGE shows comparable PRE to both the Jicamarca ISR and ICON observations. There appears to be a discrepancy between the Jicamarca ISR and ICON IVM with the later showed PRE about two times larger (∼40 m/s). This is the first time that MAGE is used to simulate the PRE. The results show that the MAGE can simulate the PRE well and are mostly consistent with observations.

Performance evaluation of IRI, IRI Plas and SAMI2 during the consecutive prolonged solar minimum of cycles 23 and 24 around 100°E

We have examined the performance of the International Reference Ionosphere (IRI 2016), International Reference Ionosphere extended to Plasmasphere (IRI-Plas 2017), and Sami2 is Another Model of the Ionosphere (SAMI2) models for long and deep solar minimum quiet time period around 100°E by comparing the models with the total electron content (TEC) obtained from a chain of Global Navigation Satellite Systems receivers. Results of the study reveal that; all the models overestimate the observed TEC for all stations and seasons, with the highest overestimation shown by IRI Plas. The IRI 2016 model performed better for all stations and seasons than IRI Plas. IRI Plas 2017 model is also simulated by assimilating the TEC derived from GPS (GPS-TEC) and Global Ionospheric Map (GIM-TEC) into the model code. The “no input” option of the model is used as a reference to study the effect of data assimilation on the model's efficacy. It is observed that the assimilation of GPS TEC and GIM-TEC into the model code reproduces TEC quite well for all the quiet days considered during both solar minima. IRI-Plas and IRI 2016 simulation is also compared with SAMI2 simulations for the same space–time configuration. SAMI2 also overestimates the quiet time GNSS TEC during daytime peak hours in all northern and southern hemisphere. Changes are made to the SAMI2 model inputs based on previously reported changes during deep solar minimum. By changing the ionizing EUV, neutral thermospheric composition, and neutral temperature, a good agreement between the simulated and measured data is obtained. However, due to strong tidal effects during low solar activity, additional modifications may be needed to the neutral density, temperature, and EUV. The drift model used in SAMI2 should also be replaced or modified for the low solar activity periods.

Multi-instrumental analysis of the day-to-day variability of equatorial plasma bubbles

This paper presents a multi-instrument observational analysis of the equatorial plasma bubbles (EPBs) variation over the American sector during a geomagnetically quiet time period of 07–10 December 2019. The day-to-day variability of EPBs and their underlying drivers are investigated through coordinately utilizing the Global-scale Observations of Limb and Disk (GOLD) ultraviolet images, the Ionospheric Connection Explorer (ICON) in-situ and remote sensing data, the global navigation satellite system (GNSS) total electron content (TEC) observations, as well as ionosonde measurements. The main results are as follows: 1) The postsunset EPBs’ intensity exhibited a large day-to-day variation in the same UT intervals, which was fairly noticeable in the evening of December 07, yet considerably suppressed on December 08 and 09, and then dramatically revived and enhanced on December 10. 2) The postsunset linear Rayleigh-Taylor instability growth rate exhibited a different variation pattern. It had a relatively modest peak value on December 07 and 08, yet a larger peak value on December 09 and 10. There was a 2-h time lag of the growth rate peak time in the evening of December 09 from other nights. This analysis did not show an exact one-to-one relationship between the peak growth rate and the observed EPBs intensity. 3) The EPBs’ day-to-day variation has a better agreement with that of traveling ionospheric disturbances and atmospheric gravity waves signatures, which exhibited relatively strong wavelike perturbations preceding/accompanying the observed EPBs on December 07 and 10 yet relatively weak fluctuations on December 08 and 09. These coordinate observations indicate that the initial wavelike seeding perturbations associated with AGWs, together with the catalyzing factor of the instability growth rate, collectively played important roles to modulate the day-to-day variation of EPBs. A strong seeding perturbation could effectively compensate for a moderate strength of Rayleigh-Taylor instability growth rate and therefore their combined effect could facilitate EPB development. Lacking proper seeding perturbations would make it a more inefficient process for the development of EPBs, especially with a delayed peak value of Rayleigh-Taylor instability growth rate.

Implementation of noise-reduction strategies and designated quiet time in an intensive care unit

Background/Aims Excessive noise is a considerable problem in intensive care units, interfering with patient rest, recovery times and patient satisfaction. This quality improvement project aimed to implement and evaluate noise-reduction strategies in a coronary intensive care unit in Doha, Qatar. Methods Rapid plan-do-study-act cycles were used to implement several noise reduction strategies, including the introduction of two designated quiet time periods per day (15:00–16:00 and 2:00–4:00), staff education about the impact of noise, environmental adjustments and an audio-visual device to alert staff, patients and visitors of excessive noise levels. A sound metre app was used to measure noise levels for 4 months before the intervention and for nearly 3 years (April 2018–December 2020) after implementation. Surveys were used to collect informal feedback from staff and patients on the ward. Results The average pre-intervention noise level on the unit were 64.6 dB, which was reduced to a consistent average of 24 dB during designated quiet times following the interventions. No adverse effects on communication or medical errors were observed. Patient and staff feedback was positive, with most patients (n=50) and all staff (n=86) being satisifed with the noise levels following the intervention. Conclusions Although the nature of activity in intensive care units makes them noisy environments, it is possible to reduce noise levels by targeting modifiable factors and implementing simple measures, such as dedicated quiet times, staff education and audio-visual noise alerts.

Observations of Night‐Time Equatorial Ionosphere Structure With the FPMU on Board the International Space Station

AbstractElectron density measurements from the Floating Potential Measurement Unit (FPMU) onboard the International Space Station allow us to observe the structure of the equatorial ionosphere. During two geomagnetically quiet time periods, we examined the equatorial F‐region structure at night using FPMU electron density measurements along with Swarm spacecraft electron density measurements and Total Electron Content from ground‐based Global Navigation Satellite System receivers for comparison. During these time periods, the equatorial ionization anomaly (EIA) extended to local times late as post‐midnight in some cases. The EIA occurrences at night showed a longitudinal dependence. The mean density of the EIA peaks exhibited a 3‐wave pattern in longitude likely due to lower atmospheric planetary wave activity, similar to the longitudinal dependence previously observed in the EIA.

The Seismic Hazard Implications of Declustering and Poisson Assumptions Inferred from a Fully Time-Dependent Model

ABSTRACT We use the Third Uniform California Earthquake Rupture Forecast (UCERF3) epidemic-type aftershock sequence (ETAS) model (UCERF3-ETAS) to evaluate the effects of declustering and Poisson assumptions on seismic hazard estimates. Although declustering is necessary to infer the long-term spatial distribution of earthquake rates, the question is whether it is also necessary to honor the Poisson assumption in classic probabilistic seismic hazard assessment. We use 500,000 yr, M ≥ 2.5 synthetic catalogs to address this question, for which UCERF3-ETAS exhibits realistic spatiotemporal clustering effects (e.g., aftershocks). We find that Gardner and Knopoff (1974) declustering, used in the U.S. Geological Survey seismic hazard models, lowers 2% in 50 yr and risk-targeted ground-motion hazard metrics by about 4% on average (compared with the full time-dependent [TD] model), with the reduction being 5% at 40% in 50 yr ground motions. Keeping all earthquakes and treating them as a Poisson process increases these same hazard metrics by about 3%–12%, on average, due to the removal of relatively quiet time periods in the full TD model. In the interest of model simplification, bias minimization, and consideration of the probabilities of multiple exceedances, we agree with others (Marzocchi and Taroni, 2014) that we are better off keeping aftershocks and treating them as a Poisson process rather than removing them from hazard consideration via declustering. Honoring the true time dependence, however, will likely be important for other hazard and risk metrics, and this study further exemplifies how this can now be evaluated more extensively.

GPS TEC variations under quiet and disturbed geomagnetic conditions during the descending phase of 24th solar cycle over the Indian equatorial and low latitude regions

• Quiet time seasonal trend in TEC is not seen during disturbed periods of low solar activity. • TEC difference between disturbed and quiet time periods is higher during the moderate solar activity. • The correlation of day maximum TEC with F 10.7 is found to be reduced during disturbed periods. The present study is focused to understand the geomagnetic storm effects on the short- and long-term variations of ionospheric Total Electron Content (TEC) over the equatorial and low latitude sectors. GPS-TEC observations over a near equatorial station Bangalore and low latitude stations Waltair and Hyderabad during the declining phase of the 24th solar cycle (2015–2019) is analysed. The TEC variations during quiet and disturbed conditions are individually analysed to understand the geomagnetic storm effects on the diurnal, seasonal and solar activity variations. The seasonal variations of disturbed time TEC are following the quiet time trend with equinoctial maximum and summer minimum in the moderate solar activity periods. But, during low solar activity periods, the seasonal dependence of disturbed time TEC is different than that of quiet time. The difference in TEC during disturbed and quiet times is higher during moderate solar activity than that of low solar activity conditions. The TEC difference between disturbed and quiet periods is found to be maximum during summer months of moderate solar activity periods. Further, correlation analysis between F 10.7 cm solar flux and TEC during quiet and disturbed conditions is carried out for three different locations. It is found that the correlation between TEC and F 10.7 cm solar flux is higher during quiet time compared to that during disturbed periods with more correlation at the equator than at low latitudes.

Superthermal Electron Deposition on the Mars Nightside During ICMEs

AbstractSuperthermal electron precipitation is one of the main sources supporting the Mars nightside ionosphere. It is expected that solar wind electron fluxes are to increase significantly during interplanetary coronal mass ejections (ICMEs) and therefore an enhanced nightside ionospheric density. This study is to quantify the variation of the precipitating and deposited electron fluxes during five extreme ICMEs encountered by Mars Global Surveyor (MGS). We find that energy fluxes correlate better with the upstream dynamic pressure proxy than number fluxes and electron fluxes increase more at high energies, which means that electrons tend to have a lower peak production altitude during storm times. The precipitating and net/deposited fluxes are increased up to an order of magnitude from low to high dynamic pressures. The estimated total electron content (TEC) is a few times of 1014 m−2 for quiet times and on the order of 1015 m−2 for storm times, with an enhancement up to an order of magnitude locally near strong crustal fields. Crustal magnetic fields have an effect on the deposited fluxes with more prominent magnetic reflection over strong magnetic fields during quiet periods, which is significantly reduced during storm times. Lastly, we estimate a global energy input from downward fluxes of 1.1 × 108 and 5.5 × 108 W and the globally deposited energy from net fluxes of 2.0 × 107 and 1.6 × 108 W for quiet and storm time periods, a factor of 5 and 8 enhancement globally, respectively, but up to an order of magnitude locally near strong crustal fields.

Magnetohydrodynamic Seismology of Quiet Solar Active Regions

Abstract The ubiquity of recently discovered low-amplitude decayless kink oscillations of plasma loops allows for the seismological probing of the corona on a regular basis. In particular, in contrast to traditionally applied seismology that is based on the large-amplitude decaying kink oscillations excited by flares and eruptions, decayless oscillations can potentially provide the diagnostics necessary for their forecasting. We analyzed decayless kink oscillations in several distinct loops belonging to active region NOAA 12107 on 2010 July 10 during its quiet time period, when it was observed on the west limb in extreme ultraviolet by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory. The oscillation periods were estimated with the use of the motion magnification technique. The lengths of the oscillating loops were determined within the assumption of its semicircular shape by measuring the position of their footpoints. The density contrast in the loops was estimated from the observed intensity contrast accounting for the unknown spatial scale of the background plasma. The combination of those measurements allows us to determine the distribution of kink and Alfvén speeds in the active region. Thus, we demonstrate the possibility of obtaining seismological information about coronal active regions during the quiet periods of time.

Electron Bulk Surface Density Variability in Ionosphere during Quiet Days at Low Latitudes

This work deals with electron surface density time variation in ionosphere region. The study uses international reference ionosphere (IRI) model for investigation. Total Electron Content (TEC) parameter is carried out at different levels in the F2-layer of ionosphere. The study takes place at Ouagadougou station (12,4°N and 358,5°E), in West Africa. Quiet time periods of solar cycle 22 are considered. This study considers only the maximum and minimum phases of solar cycle 22. The five quietest days of the characteristic months in each season are used in the study. Seasonal time profiles of ionosphere parameters highlight relation between Total Electron Content (TEC) and Height of F2-layer (hmF2) in ionosphere region. The results found in this study correlate closely with parameters behavior previously found in other works.

Energy spectra of carbon and oxygen with HELIOS E6

Context. Anomalous cosmic rays (ACRs) are well-suited to probe the transport conditions of cosmic rays in the inner heliosphere. We revisit the HELIOS data not only in view of the upcoming Solar Orbiter experiment but also to put constraints on particle transport models in order to provide new insight into the boundary conditions close to the Sun. Aims. We present here the energy spectra of galactic cosmic ray (GCR) carbon and oxygen, as well as of ACR oxygen during solar quiet time periods between 1975 to 1977, utilizing both HELIOS spacecraft at distances between ~0.3 and 1 AU. The radial gradient (Gr ≈ 50%/AU) of 9–28.5 MeV ACR oxygen in the inner heliosphere is about three times larger than the one determined between 1 and 10 AU by utilizing the Pioneer 10 measurements. Methods. The chemical composition as well as the energy spectra have been derived by applying the dE∕dx − E-method. In order to derive these values, special characteristics of the instrument have been taken into account. Results. A good agreement of the GCR energy spectra of carbon and oxygen measured by the HELIOS E6 instrument between 0.3 and 1 AU and the Interplanetary Monitoring Platform (IMP) 8 at 1 AU was found. For ACR oxygen, we determined a radial gradient of about 50%/AU that is three times larger than the one between 7 and 14 AU, indicating a strong change in the inner heliosphere.

Causes of the mid-latitudinal daytime NmF2 semi-annual anomaly at solar minimum

Ionospheric ionosonde and radar observations and theoretical calculations of the F2-layer peak altitude, hmF2, and number density, NmF2, over Millstone Hill during winter, spring, summer, and autumn geomagnetically quiet time periods at low solar activity are used to study the causes of the observed daytime NmF2 semi-annual anomaly. It follows from the model simulations that this anomalous phenomenon arises in the ionosphere mainly as a result of seasonal variations of the following atmospheric parameters: (1) the plasma drift along geomagnetic field lines due to corresponding changes in neutral wind components, (2) temperature and number densities of the neutral atmosphere, and (3) an optical thickness of the atmosphere caused by the dependence of the solar zenith angle on the day of the year for the same solar local time. Seasonal variations of the production rate unexcited O+ ions due to chemical reactions involving electronically excited O+ ions contribute to the formation of the NmF2 semi-annual anomaly during the predominant part of the existence time of this anomalous phenomenon. However, these seasonal variations are not significant, and this mechanism should be considered only as an additional source of the NmF2 semi-annual anomaly during its time of existence. The reactions of unexcited O+ ions with vibrationally excited N2 and O2 cause only weak changes of NmF2 and these changes are close in magnitude at a given solar local time during the winter, spring, summer, and autumn daytime conditions under consideration. Ignoring these reactions cannot produce a significant impact on the formation of the NmF2 semi-annual anomaly.

Characterizing Local Variability in Long‐Period Horizontal Tilt Noise

ABSTRACT Horizontal seismic data are dominated by atmospherically induced tilt noise at long periods (i.e., 30 s and greater). Tilt noise limits our ability to use horizontal data for sensitive seismological studies such as observing free earth modes. To better understand the local spatial variability of long‐period horizontal noise, we observe horizontal noise during quiet time periods in the Albuquerque Seismological Laboratory (ASL) underground vault using four small‐aperture array configurations. Each array comprises eight Streckeisen STS‐2 broadband seismometers. We analyze the spectral content of the data using power spectral density and magnitude‐squared coherence ( γ 2 ‐coherence). Our results show a high degree of spatial variability and frequency dependence in the long‐period horizontal wavefield. The variable nature of long‐period horizontal noise in the ASL vault suggests that it might be highly local in nature and not easily characterized by simple physical models when overall noise levels are low, making it difficult to identify locations in the vault with lower horizontal noise. This variability could be limiting our ability to apply coherence analysis for estimating horizontal sensor self‐noise and could also complicate various indirect methods for removing long‐period horizontal noise (e.g., collocated rotational sensor or microbarograph).

Using OpenGGCM to Compute and Separate Magnetosphere Magnetic Perturbations Measured on Board Low Earth Orbiting Satellites

We use Open Geospace General Circulation Model (OpenGGCM) simulations to predict magnetic field perturbations at Low Earth Orbiting (LEO) satellites such as Swarm, at high latitudes. The simulations allow us to separate three different major contributions to the observed perturbations, i.e., the perturbations caused by currents in the outer magnetosphere, field-aligned currents (FACs), and the currents flowing in the ionosphere. We find that at an altitude of 500 km the strongest contribution comes from FACs, followed by the perturbations caused by the ionospheric currents, while the magnetospheric currents make only a minor contribution. The high latitude perturbations do not average out over extended quiet time periods. There are significant variations in the patterns; however, on a large scale, the basic shape of the pattern remains stable. Thus, without explicitly removing the perturbations from the data, any spherical harmonics fit is expected to incur a bias. Although the predicted OpenGGCM perturbations do not compare particularly well with Swarm data, the simulations reproduce the overall pattern. However, they may still be useful to reduce the bias of the ensemble and produce better global spherical harmonic fits, by producing an ensemble whose external field contributions average out. Since this paper only scratches the surface of the role that models of the external field can play in producing unbiased internal field models, much progress is still possible, for example by improving the external model, investigating larger ensembles, and by considering data from geomagnetically disturbed times.

Influence of Atmospheric Solar Radiation Absorption on Photodestruction of Ions at D-Region Altitudes of the Ionosphere

The influence of atmospheric solar radiation absorption on the photodetachment, dissociative photodetachment, and photodissociation rate coefficients (photodestruction rate coefficients) of O−, Cl−, O2 −, O3 −, OH−, NO2 −, NO3 −, O4 −, OH−(H2O), CO3 −, CO4 −, ONOO−, HCO3 −, CO3 −(H2O), NO3 −(H2O), O2 +(H2O), O4 +, N4 +, NO+(H2O), NO+(H2O)2, H+(H2O) n for n = 2–4, NO+(N2), and NO+(CO2) at D-region altitudes of the ionosphere is studied. A numerical one-dimensional time-dependent neutral atmospheric composition model has been developed to estimate this influence. The model simulations are carried out for the geomagnetically quiet time period of 15 October 1998 at moderate solar activity over the Boulder ozonesonde. If the solar zenith angle is not more than 90° then the strongest influence of atmospheric solar radiation absorption on photodestruction of ions is found for photodissociation of CO4 − ions when CO3 − ions are formed. It follows from the calculations that decreases in the photodestruction rate coefficients of ions under consideration caused by this influence are less than 2 % at 70 km altitude and above this altitude if the solar zenith angle does not exceed 90°.

First analyses of the iOSG-type superconducting gravimeter at the low noise underground laboratory (LSBB URL) of Rustrel, France

In the last few years, the performance of the cryogenic gravity instruments has been further improved by the development of a new generation of superconducting gravimeter (SG): the so-called iOSG which is a superconducting gravimeter designed for observatory purpose with a heavier sphere than previous SGs. The first iOSG (iOSG-024) has been installed in July 2015 at the LSSB low background noise underground research laboratory in Rustrel (France), funded by the EQUIPEX MIGA (Matter wave-laser based Interferometer Gravitation Antenna) project and by the European FEDER 2006-2013 PFM LSBB – Developpement des qualites environnementales du LSBB . This instrument is operational since September 2015. We present the first tidal analyses of the 7-month time-varying gravity records of this newly installed instrument as well as the calibration results performed by parallel FG5 absolute gravity measurements. We also show the performances of iOSG-024 in terms of noise levels in the seismic (in the millihertz frequency range) band using a standardized procedure based on the computation of the residual power spectral densities over a quiet time period. The obtained noise levels are compared with other SG sites and with seismological reference noise models. The combination of the instrumental performance of the iOSG with the LSBB site properties makes this gravimetric station one of the quietest in the world, comparable to the lower sensor of the OSG-56 at BFO, at seismic frequencies.

Diurnal variation of winter F region ionosphere for solar minimum at both Zhongshan Station, Antarctica, and Svalbard Station, Arctic

AbstractDiurnal variation features of wintertime F2 peak electron density (NmF2) representative for solar minimum at both Zhongshan station, Antarctica, and Svalbard station are compared and analyzed. Both stations are located around cusp latitude and are almost on the same geomagnetic meridian plane in both hemispheres. For quiet time period, typical NmF2 diurnal variation features at Svalbard station show double peaks with a decrease of NmF2 around magnetic local noon (~UT + 3 h); NmF2 diurnal variation at Zhongshan station shows one major peak around magnetic local noon (~UT + 1.75 h), followed by a sharp decrease of NmF2, and a subpeak around 1500 UT. Simulation results of the high‐latitude ionospheres in both hemispheres agree well with observations at both stations. It is found that the major difference of NmF2 variation between both stations can be explained by the unique location of each station relative to the sunlit demarcation line during the day. For quiet time period, photoionization from lower latitude contributes to the major peak of NmF2 in the diurnal variation at Zhongshan station, while the interaction between horizontal convection and auroral precipitation is the main cause for NmF2 variation at Svalbard station. For active time period, both stations show the increase of NmF2 due to transportation of higher plasma density from lower latitudes on the dayside with the expansion of the polar cap and the additional ionization from soft‐precipitating electrons.

SOLAR WIND ∼20–200 keV SUPERHALO ELECTRONS AT QUIET TIMES

High-energy superhalo electrons are present in the interplanetary medium (IPM) even in the absence of any significant solar activity, carrying important information on electron acceleration in the solar wind. We present a statistical survey of ~20–200 keV superhalo electrons measured at 1 AU by the WIND 3D Plasma & Energetic Particle instrument during quiet-time periods from 1995 January through 2013 December. The selected 242 quiet-time samples mostly occur during the rising, maximum and decay phases of solar cycles. The observed omnidirectional differential flux of these quiet-time superhalo electrons generally fits to a power-law spectrum , with β ranging from ~1.6 to ~3.7 and the integrated density nsup ranging from 10−8 to 10−5 cm−3. In solar cycle 23 (24), the distribution of β has a broad maximum between 2.4 and 2.8 (2.0 and 2.4). Both β and the logarithm of nsup show no obvious correlation with sunspot number, solar flares, solar wind core population, etc. These superhalo electrons may form a quiet-time energetic electron background/reservoir in the IPM. We propose that they may originate from nonthermal processes related to the acceleration of the solar wind such as nanoflares, or could be formed in the IPM due to further acceleration and/or long-distance propagation effects.

Generation of Artificial Acoustic-Gravity Waves and Traveling Ionospheric Disturbances in HF Heating Experiments

We report the results of our ionospheric HF heating experiments to generate artificial acoustic-gravity waves (AGW) and traveling ionospheric disturbances (TID), which were conducted at the High-frequency Active Auroral Research Program facility in Gakona, Alaska. Based on the data from UHF radar, GPS total electron content, and ionosonde measurements, we found that artificial AGW/TID can be generated in ionospheric modification experiments by sinusoidally modulating the power envelope of the transmitted O-mode HF heater waves. In this case, the modulation frequency needs to be set below the characteristic Brunt–Vaisala frequency at the relevant altitudes. We avoided potential contamination from naturally-occurring AGW/TID of auroral origin by conducting the experiments during geomagnetically quiet time period. We determine that these artificial AGW/TID propagate away from the edge of the heated region with a horizontal speed of approximately 160 m/s.

Comparison of the performances of different spring and superconducting gravimeters and STS-2 seismometer at the Gravimetric Observatory of Strasbourg, France

Since 1973, the Gravimetric Observatory of Strasbourg (France) is located in an old fort named J9 and has been the place for various gravity experiments. We present a comparison of the noise levels of various instruments that are or were continuously recording at J9, including the LaCoste&Romberg Earth-Tide Meter ET-5 (1973–1985), the GWR Superconducting Gravimeter TT-T005 (1987–1996), the Superconducting Gravimeter C026 (since 1996), the STS-2 seismometer (since 2010) and the LaCoste&Romberg ET-11 (continuously since October 2010). Besides these instruments, the J9 Observatory has hosted temporary gravity experiments with the Micro-g LaCoste Inc. gPhone-054 (May–December 2008 and May–September 2009) and the Micro-g LaCoste Inc. Graviton-EG1194 (June–October 2011). We include also in the comparison the absolute gravimeter Micro-g FG5 #206 which is regularly performing absolute gravity measurements at J9 since 1997 and a spring gravimeter Scintrex CG5 which recorded at J9 between March 2009 and February 2010. We present the performances of these various instruments in terms of noise levels using a standardized procedure based on the computation of the residual power spectral densities over a quiet time period. The different responses to atmospheric pressure changes of all the instruments are also investigated. A final part is devoted to the instrumental self-noise of the SG C026, STS-2 and L&R ET-11 using the three channel correlation analysis method applied to 1-Hz data.